When some recovers from a disease their body creates antibodies to make them immune from that particular strain, like a particular strain of flu. So people who recovered from coronavirus have antibodies protecting them from SARS-CoV-2 so they cannot get infected by that particular strain again. Still, they should practice social distancing to avoid carrying the virus and infecting another person with it.
Regarding coronavirus, there is no exact evidence that people who have been ill with them develop immunity.
Yes, they have antibodies that help fight the virus. But it is also known about cases of REPEATED virus infection, which casts doubt on the issue of immunity.
The main thing is that after a person has recovered, the virus in him dies, which means that he can safely contact with other people.