There are three basic forms of watercolors available in stores.
Watercolor tubes have a paste-like consistency. They are already moist in the tube itself.
Watercolors in pan form are dry pigments separated in different small compartments.
Watercolor pencils are usually used to draw the initial sketch, as they can be removed with a moist brush or cloth. But you may also finish your entire painting using only them.
Tip: if you are not exactly sure of which type to get, consider buying a beginner set of each one to see which one you like best. Beginner sets are much cheaper than professional-level paints.