Because the .NET framework supports multiple languages within the platform, it defines a Common Type System (CTS). The CTS defines the basic data types that IL understands. Each .NET compliant language should map its data type to these standard data types. This makes it possible for the 2 languages to communicate with each other by passing/ receiving parameters to and from each other. For example: CTS defines a type, Int32, as integral data type of 32 bits (4 byte) which is mapped by C# through int and VB.net through its Integer data type.