The FLI has two predefined array types: the :c-array type, which corresponds to C arrays, and the :foreign-array type. The two types are the same in all aspects but one: if you attempt to pass a :c-array by value through a foreign function, the starting address of the array is what is actually passed, whereas if you attempt to pass a :foreign-array in this manner, an error is raised.
For examples on the use of FLI arrays refer to :c-array and :foreign-array in Type Reference.