A collection column is declared using the collection type, followed by another type, such as int or text, in angle brackets. For example, you can create a table having a list of textual elements, a list of integers, or a list of some other element types.
Collection types cannot currently be nested. For example, you cannot define a list within a list:
list<list<int>> \\not allowed
Currently, you cannot create an index on a column of type map, set, or list.