What is a 'List' variable type? The List<T> is a data structure part of the System.Collections.Generic namespace consisting of objects of the same data type. The '<T>' represents the type of elements in the list, for example strings or integers. Each object has a fixed position in the list, and thus it can be accessed by the specific index. Additionally, it provides methods for searching, sorting, and manipulating lists. What is an 'IList' variable type? The IList is actually an Interface. In other words, it is a collection of objects that can be accessed individually by their specific indexes. As in the case of List, the '<T>' represents the type of elements in the list. The IList<T> generic interface is a descendant of the ICollection<T> generic interface and is the base interface of all generic lists. Both List and IList type of variables can be initialized with 'new list (of...)'. For example, if we have a List ...