Understanding the update

Hello

I would like if someone can explain for me the meaning for the following lines in the .git/config (how I can understand them):

[core]
repositoryformatversion = 0
filemode = true
bare = false
logallrefupdates = true
[remote “upstream”]
url = GitHub - frappe/erpnext: Free and Open Source Enterprise Resource Planning (ERP)
fetch = +refs/heads/master:refs/remotes/upstream/master
[branch “master”]
remote = upstream
merge = refs/heads/master

For example: what heads mean and what refs mean and how all of these lines together are giving a meaning?

Regards
Bilal

You should read up on git to get an understanding of this.

Agree. But I need a little bit advise to know from where I can start.
Or even some basic information.
Regards
Bilal

http://www.lmgtfy.com/?q=git+refs+heads