Sets are unordered, distinct expressions and are defined with braces.
Lists are ordered sequences of expressions and appear enclosed in square brackets. Since there is an order to sets, we can extract the kth expression in them. Session 3.1 shows several sets and lists and some properties of each. Indexing to locate individual elements in a1 is accomplished by first extracting a list from the outermost list and then getting an element in that list. A very general arrangement of information in Maple is called a table.