ASN.1 is a fundamental tool for use by applications. It provides the ability to describe the information that will be exchanged independent of the way that information is represented on each of the communicating systems.
ASN.1 provides application and protocol developers a high-level tool, essentially a data-definition language, for defining protocol syntax and the information that an application exchanges between systems. The ASN.1 description of data is converted into data definitions in the language used locally for the application development. The syntax of ASN.1 has much in common with the declaration part of a programming language in defining, declaring and assigning values to data types and for creating complex types from simple ones.