WorldEdit works across many Minecraft modding platforms. This implies that WorldEdit’s API does not use any platform’s API types, such as Bukkit’s Player or Sponge’s World. Instead, WorldEdit has its own set of API types, and the platform-specific library (see API Libraries) contains an adapter class to turn the platform’s API types into WorldEdit’s API types, and vice versa. For example, you can turn an org.bukkit.entity.Player into a com.sk89q.worldedit.entity.Player like so

org.bukkit.entity.Player player = /* get a player */;
Player wePlayer = BukkitAdapter.adapt(player);

Nearly every other WorldEdit type (such as World, BlockVector3, or BlockState) has a similar conversion to and from the platform type. These are best discovered by looking at the methods in the adapter classes in your IDE.