For example, I have a Pentium 4 3.4GHz processor. Because of this, I set -march=pentium4 in my use flags. When I compiled everything for my system, it included this use flag. What it does is provides the capability to run extensions of the specified architecture (and breaks compatibility with other architectures), so all of the software can take full advantage of Pentium 4's power and run as efficiently as possible without worrying about backwards compatibility.
I'm just wondering what people like about it so much? I've heard tyhat its 'customisable' many times, but how is it so?
Of course, this was only an example, and you can compile your system to only support the specific hardware and components that your system has without it being bloated with random drivers for hardware you don't have, for example. Additionally, during the installation, you only install the software you want and nothing else - unlike most other distrobutions, Gentoo doesn't bundle software that not everyone uses - you select everything you want and nothing you don't.
One other great thing about Gentoo - it's ease of upgrading everything on your system. Just run this command to scan your entire computer for updates, download the sources, and compile them locally (again with your use flags) to keep your system up to date:
emerge --update world
Except for running Knoppix two or three times, Gentoo was my first distro. I admittedly had to start the installation over again a couple times, but it wasn't because I didn't understand the guide; it was just because I didn't read it carefully enough. Once I did finish the installation, I did so with a significant knowledge of the fundamentals of Linux, just by closely following the installation guide.
Don't you think i didn't do that?
Yes i got it installed, it ran like it should, but that doesn't change the fact that it's too difficult for a beginner (knowing which stage to download is one example). You should keep in mind that you need a basic linux understanding before you can actually understand the installation guide for gentoo.