If you're just getting started in the gym, you don't need a twelve-exercise routine to make progress. Five compound movements — the squat, deadlift, bench press, overhead press, and row — train nearly every major muscle group and give you the most return for the time you spend training.
Compound lifts move more than one joint at a time, which is what separates them from isolation exercises like a bicep curl. A squat bends the hips, knees, and ankles together; a row bends the shoulders and elbows together. Because more muscle mass is involved, compound lifts let you handle more total weight, which is a bigger stimulus for both strength and muscle growth than most isolation work.
A simple starting structure looks like this: three sessions a week, with a squat, a press (bench or overhead, alternating), and a pull (deadlift or row, alternating) in every session. Two to three sets of five to eight reps per lift is enough to start. The goal in the first few months isn't variety — it's consistency and small, steady increases in the weight on the bar.
Form comes before load. A lighter squat with a controlled bar path and a full range of motion builds more usable strength, and is safer, than a heavier squat cut short. If you're new to a lift, it's worth spending a session or two with just the empty bar to groove the pattern before adding weight.