When do you file 83b elections? And how does it work exactly?

I am incorporating a Delaware C-corp. I am a solo founder (at the moment) So I will buy and own all of the stock of the company. So at the moment I don't need to file a 83B election right?

However later on, if I bring on a Co-founder who's equity will be subject to vesting. When that Co-founder comes on then they will have to file an 83B election?

Can someone please explain this in detail for me, for my situation? It would be greatly appreciated.

Thanks in advance !