When it comes to weight training, the "main" workout exercises are widely accepted to be the core compound moves - that is, deadlifts, squats, lunges, and so on.
According to the Columbia Association, compound moves simply refer to any singular workout moves that uses more than one muscle group at a time. "Consider a squat," they share on their site. "This one simple motion engages your core, quads, hamstrings, glutes, calf muscles and hip flexors."
Isolation exercises, on the other hand, focus on just one muscle group (think a bicep dip or curl).