What is the difference between SSH keys for a server?

Question

linux

Comrades, many people know key generators, such as PuTTY Keygen, and they allow you to generate different types of key pairs:
SSH-1 (RSA)
SSH-2 RSA
SSH-2 DSA
There are already a few questions:
1. What difference does it make to the server what key is fed to it? Those. Is the server configured exclusively for one of the listed types, or can it be fed everything and must it accept this key?
2. What is the difference between these keys? (preferably on the fingers, because I'm a beginner)
3. Some materials for a deeper dive into the topic of setting up these keys on the server (preferably in Russian, because I have never read English technical literature, but apparently I will have to) .
Background of the questions (for those who are interested): today is the first day I started studying server administration, I got a server with authorization by key, to which I had to give access to one person. I started digging materials - with several attempts I made a key, issued the rights and accesses that I needed, but I could not repeat the success, although I did the same. I feel very uncomfortable after this. Just finally.)
Yes, by the way, who can coach on this topic (and not only this one, I'm interested in the whole Linux as far as web development is concerned) - whistle, I'm capable, I'm almost not dumb, and we'll find money. )

Answer 1

Just don't use SSH-1. Everything.

Answer 2

SSH-1 is outdated and does not provide sufficient protection, RSA is considered insufficiently reliable with a key length less than 2048, DSA is similarly what to use is a personal choice.