Devil Fruits are fruits that can give you special abilities by consuming them. Devil fruits are separated into three categories Logia, Paramecia, and Zoan.
The first category I will talk about are Logia type Devil Fruits. Logia Devil Fruits are the rarest of the three. Those who have eaten a Logia Fruit are granted the ability of transforming their bodies composition into a natural element at will, as well as create and control it.
The next is Paramecia type Devil Fruits. Paramecia Devil Fruits are a more common class of Devil Fruit. Most often, they will allow the user to turn their body into a different substance, or produce a substance at will. In other cases, they will allow to user to affect the environment at will.
The last is Zoan type Devil Fruits. Zoan type Devil fruits are very rare but very common. That is because there are two types of Zoan Fruits, regular Zoan and mythical Zoan. A regular Zoan fruit lets the user turn into a animal or animal hybrid at will. Mythical Zoan fruits are the exact same, but they are more rare and let the user transform into legendary creatures such as dragons, pheonixs, etc.
Devil Fruits can be consumed by any type of animal even though its more common for humans to eat them. You can turn into a very strong being by eating a Devil Fruit, but one major flaw is losing the ability to swim. Another fact about Devil Fruits is that when a user that has consumed a Devil Fruit dies or passes away, the nearest regular fruit will turn into an exact replica of the fruit that user ate. Devil Fruits can be very useful in times of need and are also could be used for everyday use, all the while making the show more interesting.