There are many varieties of Basal, however, the one most commonly used in cooking is Sweet Basil.  Sweet basil is grown as an annual in most climates.  It is essential to Italian cooking and some Oriental and Middle Eastern cuisines.

Basil is best used fresh.  When dried it loses most of its flavor and does about as much good as adding a hand full of torn up tissue paper.  Even when used fresh, it should be added at the end of the cooking process as it loses much of its flavor when exposed to heat for very long.

Fresh basil may be kept for a few days in the refrigerator, but it will soon turn black.  To freeze it must be lightly blanched.  You may also freeze puréeing it in the blender and adding a bit of olive oil first. 

Sweet basil is essential to a true pesto sauce.  It is a good companion to tomatoes, either fresh or when lightly cooked.

If you have a long warm growing season try growing your own, either from seed or bedding plants.

Pesto Sauce

Gnocchi with Fresh Tomato Basil Cream Sauce - The Piedmont Italy

Pasta with Fresh Tomatoes & Anchovies - Sicily, Italy