What does "root" the phone mean?
Basically it is what aileron said. To take it a little forward... the Android system is "open source" meaning the software of the phone is available to anyone to do what they want. Rooting is the process that gets you into the software.
Phones run off of roms and kernals together. Each one does something different in requires to how your phone reacts to different functions. Like phone calls, where to save contacts (phone or SD card), games,
Internet, battery usage, speed, videos, apps, and many others.
The Rom is the part that gives you control of all that stuff. Developers create Roms (since it is software) for free, that "customize" a phone more toward specific tasks.
For example, your particular usage is internet, games, Facebook, video, accounting, printing, gps nav. So a developer creates a Rom that would do those functions faster with less battery drain. So they may tweek how memory is shared what storage to use and how to tweak the "radio".
As you can imagine, there are countless uses that people would want out if their "smart phone". So this process makes it more smarter.
For that reason, there are multitudes of roms available. It takes research to find a particular Rom that meets your specific needs. Typically, there will be one available.
Like all software some work better than others. So if you "flash" a Rom and don't like it, just find another.
The neat thing is there are apps specifically made for rooted phones that allow you to do more with your phone other than just having a high dollar phone for calls and internet.
Some draw backs are, as aileron mentioned, brick your phone. If you can't read and follow directions this process is not for you. Otherwise its pretty safe, but it does take time to read and learn BEFORE you attempt it.
Also void the warranty on the phone, usually. There are ways around it.
It can be time consuming.
Hope this explains it a little more.
Check out the link I posted earlier. Tells you EVERYTHING you need to know and the some. Has all the roms, kernals, radios etc... you could ever want. Some are easy and some are more difficult if your not tech savy like me.
Your best bet, hire a vet! Please.
