The more you drive, the more you contribute
You will definitely benefit the people around you, simply by enabling Waze passively before each drive. Your current speed data (though not in Navigation mode) will contribute valuable information about traffic congestion, and to calculate optimal routes to all other users in your area.
Each type of event you report on the trip, whether it is traffic congestion, roadblocks or bad road conditions, etc., will be posted to the communities around you.
You will be awarded points / scores for each action taken, followed by increase in position which will give you access to a slightly different look for your 'mood' icon on the Waze map.
For more information, see the article on Rank and Points
Edit the Map for the Greater Good
Mapping is also a way to contribute to the effectiveness of Waze's functions and earn rewards. In order to prevent the map from being damaged by less experienced editors, the Waze community has published a step-by-step mechanism in the form of edits that will gradually increase in area, starting from small areas around your drive and on secondary roads (where minor edits do not cause major damage on map quality), followed by assigned areas and ultimately the entire country.
Further information on the edit area will be detailed on the Rank and Points article.