The Basics on Abs
The abdominal muscles or the abs make up the front and the sides of the abdominal wall. There's four main layers of muscles. The deepest layer is the transversus abdominus followed by the external and the internal obliques, which run at 90 degrees to each other. On top of that is the rectus abdominis. This is the 6-pack or the 8-pack depending upon your Anatomy. The deepest layer of the transversus abdominus exists on both sides and surf to compress the internal organs and stabilize them.
Think of this layer as a belt now when this layer contracts, it can forcefully expire air as you would do in a cough or a sneeze. The external obliques also are found on both sides. If for example, contract on this side they will bend you towards the same side or EPSA. Laterally they can also contract to rotate you to the opposite side or to the contralateral side. The internal obliques are also found on both sides. If they can track for example on this side they'll serve to bend you towards the same side or it's a lateral side. They can also rotate you to the same side or if so lateral side.
If they both contract together simultaneously they bend you and there's forward flexion at the lumbar spine and it also compresses the abdomen, the rectus, abdominis or the six-pack or a pack depending again on your anatomy serves to bring the chest towards the hips. Now here's a tip for you, if you're trying to get your abs to show and get that aesthetic look that you're looking for just remember that the rectus abdominis, the part that's going to show is a very thin layer of muscle. So you have your skin fat layer and muscular layer which is the rectus abdominis.
There's two ways where you can get that muscle to show either growing your muscle layer or shrinking the fat layer. Now again you can only grow the rectus abdominis so much so there's a primary way that you're gonna be able to show your abs of. This is by decreasing that fat layer or reducing your body fat which will require that you be in a caloric deficit meaning that you're consuming less calories than your body is burning.
The last tip I want to give you if you're working on your abs is try to avoid over engagement of your hip flexors which will serve to flex you at your hip like this and bring your knee up towards your chest. That is now engaging your abs so try to focus more on contracting your abdominal muscles and think about what you're doing so you can take the focus away from your hip flexors and put it towards your abs.