Where does it store files?

[nothingspecial]

If I understand you correctly, yes.

[JKyleOKC]

Note that if you reformat /home, you will lose all of your personalized configuration information, and even your user account. If that's what you want, fine, but many of us choose to keep our home directories intact from one install to the next.

I've done it both ways, and now retain the home directory (mostly because that's where my virtual machines are stored, in a hidden directory, and I don't want to lose all of them; I could move them to a separate saved filesystem but that would be a lot more work for no real advantage). Since you're pretty much starting from scratch, your approach should be fine.

[petrasflorin]

I prefer formating /home too because I install a lot of crappy unuseful **** that not only it is like I said crappy but it is (will) be the reason for my reinstalling of Ubuntu. Good to know the other /data partition is safe.

[florinbelea]

everytime you install a new software using apt-get or synaptic package manager,
apt stores the downloaded packages at /var/cache/apt/archives.
you can delete those archives to free up space

10x man! I was looking for a way to save the files i have installed trough the terminal i case i want to reinstall the OS i needed the firefox update just in case... anyway 10x