1.CLS (Common Language Specifications)
Its is a subset of CTS(Common Type System)

1. .Net framework support more than 70 Languages.
   Example : C#, J#, F#, VB
   Number declare in VB is : Dim a as Integer;
   Number declare in C# is : Int a;

This above differences in declaration is…. managed by CLS and CTS and
Dim a as Integer, Int a is declared in CLS as ——>> Int32 a **;
CLS have some set of rules or guidelines to satisfy the all Language Compilers in .Net Framework. Each Compilers should follow the rules to communicate with CLR. Otherwise the code will not work on properly in .Net framework or .Net Environment.

CLS and CTS is both supporting to Cross-Language Integrations.