Rest between sets
<60 secs: Increase endurance, burn more calories
1-2 mins: Building more muscle, and some endurance benefits
2-3 mins: Building more muscle and strength
3-5 mins: Pure strength and power purposes
Compound movements may be better with 1-2 mins rest, while isolation exercises with 45-90 sec rest.
Incorporate all rest intervals, because their benefits transfer across.