A sequence is an ordered collection of elements, implemented as either a vector or a list.
Sequences can be created by the function make-sequence, as well as other functions that create objects of types that are subtypes of sequence (e.g., list, make-list, mapcar, and vector).
A sequence function is a function defined by this specification or added as an extension by the implementation that operates on one or more sequences. Whenever a sequence function must construct and return a new vector, it always returns a simple vector. Similarly, any strings constructed will be simple strings.
In general, lists (including association lists and property lists) that are treated as sequences must be proper lists.