Dialogue can be used for:-
It makes the story advance. Injecting an objective into writing
Develops character - Can give emotional depth.
Increases pace and make more dynamic
Provides Information (but be careful - not too much see below).
Can be incorporated in the action scenes
Helps gives readers a more 3D sense of the scene
Helps to give a sense of place
Too big chunks of dialogue can be overwhelming and rather flat so intersperse with prose to give the reader a sense of the scene.
Make sure not to drop huge chunks of back story or other information into dialogue which won't sound like a realistic conversation.
Use Speech tags like 'He Said' 'See Said' which often the reader doesn't even notice rather than 'He growled' etc all the time.
If you can replace speech tags with nothing by making your dialogue so clear that you don't need to constantly tell the reader who is talking. Characters have a distinctive voice so the reader can easily tell who is talking.