if i wanna add an entry to a table, and the primary key is auto increment, does it mean it automatically counts up by one with every new entry?

These type of question should go into help or SQL in the future. How is your primary key setup? In dashboard UI as "Is Identity" or did you do SQL on it? If you ever have directly updated the column in the table you can get a conflict with the increment. And just FYI serial/identity increments it internal counter even on updates so count could skip for next insert.