How is a net electric charge produced?

Net charge produce due to presence of different chargers in the vicinity or in the considered region.

Explanation:

Net electric charge is just a concept introduce to identify the result of the presence of number of charges which interact with each other. It can be found by treating electric chargers in algebraic form like numbers, where + charges get added with + charges

-charges get added with - charges

and when adding two charges with opposite signs they get subtracted and the symbol of the resultant charge comes from the charge with highest magnitude.