Answer:
It is a symbol used to denote an angle (or something else)
Explanation:
Alpha(α) is a greek letter, it's one of the letters used to denote angles. Other such letters you'll often see in math are Beta (β), Gamma (γ), Delta (δ), these are used to denote angles. Also, pi (π), which is a mathematical constant. The letters phi (φ) and theta (θ) are also used for angles very often, especially in formulas. You'll see some of these in physics too.
It can be used as variable too, not necessarily for angles, but it's mostly used for them.