They all help you name a polygon, let's start with the sides.
Sides help you classify a polygon, for example if they tell you to find a square, you know that it has four sides and with that info you wouldn't choose a hexagon
Angles help you classify a polygon, for example if they tell you to find a square with four right angles, you wouldn't choose a diamond since it doesn't have right angles,
Vertices help you name a polygon, for example if they tell you to find a hexagon with six vertices, you wouldn't choose a square.