Every location—including fields, parameters, method return values, and properties—has a type, and a specification for its type is carried in metadata.
A value type describes values that are represented as a sequence of bits. A reference type describes values that are represented as the location of a sequence of bits. The CLI provides an explicit set of built-in types, each of which has a default runtime form as either a value type or a reference type. The metadata APIs can be used to declare additional types, and part of the type specification of a variable encodes the identity of the type as well as which form (value or reference) the type is to take at runtime.
Metadata tokens representing encoded types are passed to CIL instructions that accept a type (newobj, newarr, ldtoken). (See the CIL instruction set specification in Partition III.)
These encoded type metadata tokens are also embedded in member signatures. To optimize runtime binding of field accesses and method invocations, the type and location signatures associated with fields and methods are encoded into member signatures in metadata. A member signature embodies all of the contract information that is used to decide whether a reference to a member succeeds or fails.