What does fromEulerAngles do?

This is the equivalent of > CFrame.Angles.

Euler angles are all about orientation. The three input values it takes are

RX RY and RZ

The "R" stands for radians. A radian is essentially just an angle but in a different format in which one radian is the distance a circle's radius covers around the circumference of a circle.

This Short Gif really helps to explain how they work.

You don't have to have a complete understanding of radians to make a rotated part in roblox. If you prefer using just degrees, you can lua's method of turning a degree angle into a radian.

> math.rad(90); -- would be the value of one-half pi radians.

here is an example of how you would construct a simple CFrame.

local rotation = CFrame.fromEulerAngles(math.rad(25), math.rad(106), math.rad(73));
workspace.Part.CFrame = rotation

Please note that this only defines orientation. In order to add a position to a rotation you would do it like this.

local position = CFrame.new(0,25,6) -- should be a CFrame value, not Vector3
local rotation= CFrame.fromEulerAngles(math.rad(25), math.rad(106), math.rad(73));
workspace.Part.CFrame = position * rotation

Euler Angles can be used to rotate a brick from a script using CFrame.

E.g:

brick.CFrame = CFrame.Angles(math.pi, math.pi/2, math.pi)