What is the reputation? How do game measure it and what it indicates? Thank you :)

Reputation helps you in unlocking productions. Productions generate daily profits and few items that you can sell/use. Higher the reputation, higher will be the narcos that follow you which can be used in production activity. Narcos dont require any payment/salary so essentially they are free of cost resource.

Reputation can be earned by doing jobs or by attacking other players.

It is an absolute number and is visible on your profile page.