Can someone explain how people get TFSA money?

We've got a new insurance company at my job this year, and we were supposed to transfer existing RRSP contributions over to them from the old one. I haven't actually contributed to my RRSPs since...three jobs ago (over five years) so I went to check what I had saved up.

Now I understand how money gets added to my RRSPs (sort of) but how does money get added to TFSA? I googled it and some people are saying they have over 100k in there but just say they took money out of it and invested it to increase it.

Is it like...100k that the government gives you to invest as you want? Also is being in a contribution room of x dollars the same as just...having x dollars?