Bodybuilding competition = Based on how you look. Building the most complete physique muscle wise at times with as muscle as possible. Having the right muscle shape and insertion are a factor. Also being low bodyfat enough or at times being vascular or striated or have enough muscle definition and separation. You compete on stage
Powerlifting competition = Having the highest bench press, squat, and or deadlift as possible for 1 rep. You get up to 3 attempts to do a lift and a 4th attempt for an all time world record that doesn't effect the total but effects the single lift you competed in. It also has to pass certain rules and get minimum of 2 out of 3 white lights to pass but ideally you want 3 white lights each lift. That means you lifted with proper form. You compete on the platform.
Training For Both
Powerlifting vs Bodybuilding: Similarities
Bodybuilding is training an exercise for more than 6 reps or any amount of volume even sets of 1 to 5 reps for the intent of building bigger muscles
The bigger muscles build the base to build the strength
Building the muscles with the powerlifts and the variations will build the weak muscle either weak developed muscles and make them stronger so you can even get stronger for the target powerlifting exercise for the weakpoint in the exercise
Strength builds muscle and muscle builds strength
Not just for the powerlifts and the variations but other exercises that build muscle and strength and are functional.
Good to build the muscle to succeed in bodybuilding and the muscle to build the exercise weak point and get stronger in the sport of powerlifting
Powerlifting vs Bodybuilding: Differences
Powerlifting in competition you want to train the best way to get stronger at the one rep max in the bench press, the squat, the deadlift, or the best of all 3 reps.
Bodybuilding you want to build muscle in the off season and not necessarily the most muscle but your weak points you want to focus on more.
Bodybuilding is about building the complete physique and as proportional as a muscular physique as possible
When you diet and cut for bodybuilding you also want to try your best not to get injured as you will be depleted and have less fat to cushion yourself and you will eat less. So when you lift heavy weight, it's okay to as it builds and maintains muscle or you want to relieve stress but be mindful of your body and have total body awareness before you get injured
Bodybuilding training uses the big compound exercises and powerlifts but more especially nowadays also use machines. This is to get the work in and prevent injuries they would get from going hard and heavy on the main movements all the time. Also to hit the muscles in certain angles doing certain range of motion with some machines and the poly drug use will take over and its also about how much you get out of a cycle or PED protocol. Same with powerlifting if compete untested and are open about your PED use which depending on your situation it's up to you to say or not.
Also regardless of PED use you either have the genetics or not. Genetic response out of drugs also is what makes you a champion. Some people have good natural genetics even more than those who are genetically average or below average without PEDs but because the average and below average genetic people took drugs, got a good response from PEDs, and trained the right way, they become champions. Some people with good natural genetics get very little out of PEDs or don't become champion because they already were so good without PEDs they are already close to their limit. The average PED user looks natural or has below average, bad, or average genetics and took PEDs and are good or above average or average at best. Then again the common person doesn't know who is natural or on PEDs and doesn't care at the end of the day and want to see someone impressive. Ideally people want to see and believe their heroes are natural which very few are natural and you can be great naturally. More information is out there on how to train, there is more coaches and federations where people have done great things naturally in strength sports and built great physiques that are naturally achievable, and you just have to do it long enough and that is a very long time it can be 10 to 20 years or more and with time know how to research better. Also truly want it for yourself and not be blinded by liars or compare yourself to others. There will always be people greater than you but that shouldn't stop you from achieving your goal or getting better.