A pennant is a flag that is larger on the hoist than the fly. In case you are not familiar with the anatomy of the flag. The hoist is the half or edge of the flag nearest to the flagpole. The fly is the half or edges farthest away from the flagpole. Just by the description, you should be able to visualize what a pennant looks like.
Pennants come in several shapes. The most common shapes are triangular, tapering, and burgee.
You can see the aforementioned shapes below.
Still, there are other shapes for pennants aside from the popular three. The Nepalese national flag is an excellent example. It is simplified double triangular pennant. It is the only national flag that is not quadrilateral. Its unique shape makes it stand out amongst other national flags.
The unique shapes of pennants which makes them more eye-catching is an important quality for promotional flags.
Aside from being unique, there are practical benefits resulting from the shape of the pennant. Its tapered shape lends itself to less wind resistance. You can have a larger-dimensioned flag without worrying about wind knocking the flagpole off its base.
And because the fly end is narrower than the hoist, it means it is also lighter. It does not require strong winds to make the flag fly through the air. This makes the pennant more attractive.