Freestyle Kicking (aka "Flutter Kick")
You want you feet pointed to the wall behind you (so your feet are flexed like you are standing on your tip toes)
This is why fins and flippers make you swim faster, because they can flick the water behind you which creates a wave of power that pushes you forward
Remember, the fastest kickers keep their feet under water the whole time
www.youtube.com/watch?v=_X6M6gEmTBE
Breaststroke Kicking (aka "Frog Kick")
You want your feet pointed to the bottom of the pool (not the wall behind you) like you are about to jump flat-footed off the water
This is why it is called froggy kick because you kick back like a frog to propel yourself forward
A good drill is to try breaststroke kick on your back and if you are doing it correctly your knees should stay under the water the whole time on your back
www.youtube.com/watch?v=Ux4oWoLCPlU&list=PLUaeqTN0mwx8sSbsVkt7399ng_tUKf3Z5&index=3
In order to swim straight, you must keep your head straight
www.youtube.com/watch?v=FgbSjsbyzfE
Make sure you know how to quickly get a breath in on the wall
www.youtube.com/watch?v=XfkKOqsfkkI&list=PLUaeqTN0mwx8sSbsVkt7399ng_tUKf3Z5&index=11