The Barbell curl is a simple and proven way to build up your Biceps.
This is an isolation exercise that primerily targets your bicep muscles. The exercise involves also your forearms and shoulders as secondary muscles, even though it's not really considered a Compound Exercise.
The barbell curl is great for begginers since it quite simple to learn and fun. Developing your biceps is easy and will make your arm looked muscular and toned quickly. Also, The biceps accounts for 1/3 of upper arm mass and needs to be developed to balance out the triceps.
Changing grip width will affect what muscle of your biceps works the most. Taking a wide grip on the barbell increases the tension on the short (inner) head of the biceps. While a narrow grip will focus more on the long (outer) head.