Hello I am new to PostgreSQL world I installed server and created DB's and created users till there good after lot of struggle now I want to know the role of PSQL command line and how to connect to client through PSQL command line and what actions I can perform doing that
psql is a command-line based client that connects to the PostgreSQL server.
The phrase "[...] and how to connect to client through psql" makes no sense.
As Jan mentioned there is excellent documentation that you should avail yourself of.