This document discusses user-defined data types in computer science, including non-composite and composite types. Non-composite types include enumerated types which define a list of possible values and pointer types which reference a memory location. Composite types include record types which collect different data types into a coherent whole, set types which define a list of unordered elements, and class types which define objects with variables and methods. The document provides examples of defining each of these data types in pseudocode.