[cbk1994]

Please work on shortening your posts, it's tempting to just ignore them because they're so laborious to read.

The degree/radians conversion was just an example of a standard function built into the language.

The reason you prefix it with this is because it is a function of that object. When you use this as the prefix for a variable, it is set only for that object (that script). You don't have to use this as a prefix for variables, but you should since it clearly shows which object the function belongs to—it's only natural since variables require the prefix. As WhiteDragon said, don't worry about this yet. Focus on understanding variables and functions, then work on object orientation.