What is "list"

A list is an abstract type of data that represents a sequence of values in order of input(add), where the same value can occur more than once. Each position has an index associated to it that allows direct access to the stored value. Typically, this structure offers the operations of "insert in list" (either at the beginning, at the end or at arbitrary positions), "remove from list", query (and perhaps replace) an element of the list given its index, scroll through the list in direct order (and perhaps inverse) of its indices, among others.

The way to implement a list has an impact on the computational complexity of each of your operations. The most common are through a array, where the size is [initially] fixed and the elements occupy contiguous memory positions, or through a chained list, where each element holds a reference (or pointer) next to the next element [at a minimum]. Other implementations are possible but not very common.