Knowing the ins and outs of a map in CS:GO can give you an advantage over your opponents. Though most one-vs-one situations will be decided by your individual talent, you can always increase your chances of winning by putting yourself in a more favorable position.
If you know the map better than your opponent, you’ll have the knowledge to anticipate their movements and plan your round accordingly. One of the best ways to learn more about the maps is by playing them. The more you play, the more you’ll understand the callouts and all aspects of the map. But you can also give yourself a headstart by studying the maps as well.
What are callouts
Callouts are used to effectively communicate map positions to your team. They are useful when you quickly need them to know where you are, where an enemy is, where you are flashing, and so on.
A good callout is preferably one or two syllables long and related to something unique about that specific area of the map. There isn't a global standard of map callouts, being able to communicate efficiently with your team is what is most important.