Join tables Logic

Hello there,

I’m not understanding the logic behind the “join tables” way.
If you are selcting columns from a table, or all (*) the columns table… then why is putting them before the columns of the joining table?

Otherwise, why can you select columns from diferents tables if you were selecting only one table FROM?

Everything has its logic, but i’m not understanding why this is so confusing. I’m cretaing inverse mental rules to understant how join command is working.