Actions in Combat. When you take your action on your turn, you can do one of the following:

• Attack 

• Cast a Spell

• Dash (gain extra movement)

• Disengage (move without provoking opportunity attacks)

• Dodge (focus on defense)

• Help (aid another in attacking or completing a task)    

• Hide (slink past a guard, sneak up on someone, etc.)

• Ready (wait for a particular circumstance before you act)

• Search (devote your attention to finding something)

• Use an Object (interact with 2 things or as required by object)

• Other Actions. You can do many other things as an action, the success of which sometimes requires an ability check. 

Many monsters have action options of their own in their stat blocks.