How to make different sessions with remote access?

Question

System administration

My friend has the following system on the service:
There is an internal server to which 12 computers are connected.
Each employee has his own computer and "username" "password".
I can’t figure it out in my head, they open the program (click twice with LMB) and the field is displayed:
"Username" and "Password", after entering, some program opens or something like where they choose which ones there sections and look for information of any kind.
The question is, how does this even happen? After all, if 3 more employees connect via "remote access", they will also see what only 1 person who first connected is doing, and they will not be able to do what they need (search for their information), how and with what program it is possible, what at each connected user to the internal server through remote access - different sessions? Tipo programs when connected are the same, but the sessions are different and everyone does what he needs.

Answer 1

1C, for example.

Answer 2

Normal terminal server. Simultaneous work of many users in remote desktop mode.