Pretty much all of the main routines focus around the main compound lifts which are bench press, overhead press, back squats, deadlifts, and bent over rows (or pull ups).
It kind of comes down to how much variation you want in your routine, and if you are focusing on body building or strength (or both).
Personally I started with Strong Lifts 5x5 which is a good intro. Has it's own app, easy to follow, and the guy who developed the program has a great website with video tutorials and written instructions for each lift. Personally I found it to be too much squatting (you do 5 sets of 5 squats every time you go, which adds up quick).
I then moved on to Greyskill LP, which is similar but instead of doing 5x5 for every lift you do 2 sets of 5 and then the last set until (almost) failure. I mixed in a bunch of accessories as well. Overall I felt this was yielding the same results as 5x5 but with less time spent in the gym each time. (once you start hitting the upper end of your strength, 5x5 begins to take between 1.5 - 2 hours each time when you account for warm ups and rest periods).
I have recently switched to 5/3/1 which is more for building mass than strength, and is a bit more complicated to keep track of.
reddit/r/fitness has a ton of good resources. It's easy to get lost in the weeds, but as long as you're hitting your main lifts and doing at least 3 sets of each, adding weight each time, you will make progress. Don't get too bogged down in adding accessories, as they are meant to help improve your weak areas when you get stuck on the main lifts.
Note to new lifters: Most important tool to buy is a spiral notebook and ballpoint pen; plan out all your exercises, sets, and weights before going to the gym, do reps for each set till muscle failure then write down the number of reps achieved, and use that historical set data to design next gym visit, this is the worlds simplest lifting program.
Another general note about "programs" is lifting is much like diet in that there are some plans that are very simple and some that are very complicated and both CAN work well although which works best for which person requires experiment. For example there are extremely complicated diet programs with incredible attention to detail and discipline, and then there's "Don't eat it if your ancestors couldn't eat it" and both can work very well (although one sells many more books than the other...).
Likewise the ridiculous simple workout plan is, on the short term, do about three sets with a five minute break in between, a warmup, max, and somewhat less than max, and on the long term plan your workouts such that you get muscle failure at over a dozen reps on the warmup set, and about 7 reps on the max set and 3rd set. Barrels of ink have been spilled on the topic of do two sets vs three sets or aim for muscle failure at exactly 15 for warmup as opposed to 12 or power lifters should max at 4 reps vs body builders should max at precisely 9 reps. All of which is probably true for various individuals in various situations. A better use of your time than reading and researching all that, is make very small changes to that, then look at your spiral notebook and see what is working for you personally.
The only other programs or rules to follow apply to all plans, its very hard to hurt yourself by moving too smooth, or too light of a weight, but the opposite is not true.
It kind of comes down to how much variation you want in your routine, and if you are focusing on body building or strength (or both).
Personally I started with Strong Lifts 5x5 which is a good intro. Has it's own app, easy to follow, and the guy who developed the program has a great website with video tutorials and written instructions for each lift. Personally I found it to be too much squatting (you do 5 sets of 5 squats every time you go, which adds up quick).
I then moved on to Greyskill LP, which is similar but instead of doing 5x5 for every lift you do 2 sets of 5 and then the last set until (almost) failure. I mixed in a bunch of accessories as well. Overall I felt this was yielding the same results as 5x5 but with less time spent in the gym each time. (once you start hitting the upper end of your strength, 5x5 begins to take between 1.5 - 2 hours each time when you account for warm ups and rest periods).
I have recently switched to 5/3/1 which is more for building mass than strength, and is a bit more complicated to keep track of.
reddit/r/fitness has a ton of good resources. It's easy to get lost in the weeds, but as long as you're hitting your main lifts and doing at least 3 sets of each, adding weight each time, you will make progress. Don't get too bogged down in adding accessories, as they are meant to help improve your weak areas when you get stuck on the main lifts.