How does CFrame.Angles(rx,ry,rz) work? Does it have anything to do with math.rad ?

A Radian is the primary unit type used when modifying orientation components of a CFrame. This unit is apart of the International System of measurements, otherwise known as the modern metric system, and is used in most mathematics. Since CFrames belong to a trigonometric family, and contains angular matrices, it is likely this unit is to be used here.

If you're unsure of what a Radian is exactly, it "is the angle made at the center of a circle by an arc whose length is equal to the radius of the circle".

That is definitely hard to grasp at first, so take a look at this GIF to get a better understanding if you wish. - Credit to @nighttimeninja314 for the source.

Radians may be confusing for some people to adjust to, or simply isn't the measurement unit they desire to use. To apply degrees when using CFrame.Angles(), we use the math.rad() function to convert this number into a suitable unit that the CFrame can accept.