Hey there! I'm happy to help!
Imagine a line going straight from the North Pole straight down to the center of the Earth. Then, imagine another line from the Equator going through the Earth and meeting the vertical line. This makes a right angle. A right angle is 90 degrees, so this means that there are 90 degrees of latitude. All of the calculations for degrees of latitude are based around this!
For example, if you move the line from the top of the North Pole to Mexico (a (Tropic of Cancer), the angle inside the Earth is 23.5 degrees. You can move this top line around to get different angles with the equator, and that's where they all come from!
Have a wonderful day and keep on learning! :D