Pastel pencils are perfect if you're looking to create controlled, detailed works of art with pastel. They're just like conventional pencils, but encased within the wood is a thin stick of pastel that has a consistency in between hard and soft pastels.
Pastel pencils are versatile enough to be used on their own but many artists also use them in combination with other pastel types (excluding oil pastels). They can be used dry or wet and can be blended just like other pastels. You can sharpen them to a point to create precise details or use them bluntly for soft, hazy lines.
Many artists also use them for preliminary sketches, which is especially handy given that graphite pencils aren't compatible with pastels.