Free Software is probably the most misunderstood term in modern computing, and understandably so given the apparent ambiguity of its meaning. Here I attempt to clarify what it means and contrast with Open Source
When I first heard this mantra, many years ago, I must admit I never really grasped its meaning.
To the casual observer Free Software implies that it is free of cost, so the mantra is used in an attempt to clear up this confusion. However I believe it has caused more confusion, especially around what exactly is meant by "freedom" in this context.
Another source of confusion is the use of the word Open Source, especially when used by companies or in a context of commerce.
Bottom line: Open Source IS NOT Free Software
Open Source simply means that source code is available. Nothing else.
So, for example, you might have source code for a version of Android (this could be pretty much any software, but just to give a concrete example), but on its own it may not work. You may need specific hardware, or binary (no source code) drivers, additional programs, specific hardware, or services in order for it to work.
To add to the confusion, Wikipedia also puts the two terms in pretty much the same category:
There are three points mentioned in the Wikipedia article that appear to put Open Source in the same category as Free Software, so I'll attempt to address them:
Point  means that, for example, an Open Source application written for Windows must not be restricted in use to the Windows Operating System. This fine, but it doesn't mean that the source code need be easily portable to another system, nor does it mean that it will function without additional proprietary services (i.e. services provided by Google, Amazon, Microsoft, Apple, etc).
The second point  is good in that supporting software must not be restricted in any way, but it doesn't prevent any limitations mentioned in the previous paragraph.
As for the final point, this is effectively the same as point , but for hardware. So, the license may not restrict the use to a specific line of devices, but the source code itself could easily be limited.
The meaning of Open Source has been used as a banner for many companies for decades now. More and more companies are coming to the realisation that to make their software Open Source implies that they are more trustworthy, and respect the people.
This is disingenuous.
All of the big names in computing use Open Source as a shield in which to make them appear honest, open and trustworthy. And for the most part this works well for them. Microsoft has appeared on the surface to be a company that is fully embracing open software, and one could argue that they are doing fantastic things for the open source community in general. This is arguably true, but it doesn't mean that their long-term goals are the same.
Companies are free to change their tactics or ideals at a whim. It's really up to the board of directors, shareholders, etc, and they want to ensure the business is profitable.
I think the most contentious aspect of Free Software, and indeed the most difficult to digest is the politically charged aspects of it. All too often, it appears that the Free Software Foundation is used as a sounding board for all left-wing politics. It's oftentimes touted alongside equal rights, discrimination or other political agenda. I feel that this also makes people feel a little uncomfortable when looking to support it.
Simply most people do not have a hard left or right agenda. It divides people, and closes lines of discussion by blurring the lines with somewhat unrelated political views.
I'm not saying that this is a bad thing per se, but I do strongly feel that Free Software should remain politically neutral. In the same way a freedom of speech - do not attempt to silence your opponents, as they may also have something valid to say.
The way I feel about Free Software is a little different. While I may have political opinions, I don't have an agenda I feel the need to push, and I am opposed to using any and all topics as a soapbox from which to preach.
The core values of Free Software to me is freedom of choice. Most of the applications I use both in work and at home are free or open source. I can update or configure them to work even more closely with my own particular workflow, and it works wonderfully.
It also adds security. If all software you use is open or free source, then it's also open to scrutiny. Security issues can be quickly identified, and it is less likely for back-doors to be present (or at least they can also be identified if present).
When there is no source code available, then there is no guarantee of security nor any guarantee that there are no developer back-doors. You are left again to trust the company producing the software
Please note that this is not limited to he obvious: there may be serious security issues buried in your devices - see Intel Management Engine)
You may not be concerned about this, or feel that it is futile to avoid all hardware and software, but there are options which I'll also discuss in my blog, but for example have a look at Purism, EOMA68, DragonBox Pandora or MNT Reform for just a few.
This is also a common misconception. I have donated quite a lot to many open source projects, bought open source applications and spent money on services, products and books. If a company reflects my moral philosophy, then essentially I will be more than happy to support them as much as I can.
Even if financial support is not possible, it is possible to help any open/free source application by helping promote, review, correct and/or update it. Free software is from the community, and for the community.
The simple message I'm attempting to convey is that Open Source has recently become something that it was not originally intended for. Time and words have twisted the original ideology, and only the Free Software Foundation remains to preserve that original philosophy. Even if, unfortunately, their intentions can sometimes get distorted with or misunderstood as hard-left politics.
The philosophy of free software, if embraced and understood, can deliver a feeling of true freedom.
I know that I am not tracked, monitored or analysed by any software on my laptop, and have also locked down the internet so I am not bombarded with adverts or malware. Everything I use from the operating system, all the way to all of the programs I have I chose to install and have configured to my preferences.
This is true (software) freedom.