ASN.1, or Abstract Syntax Notation One, is a standard interface description language used for defining data structures in a way that is independent of machine-specific encoding. It allows for the representation of complex data types, making it easier to share information between different systems and applications. ASN.1 is widely used in telecommunications, networking, and cryptography, among other fields. It supports various encoding rules, such as BER (Basic Encoding Rules) and DER (Distinguished Encoding Rules), which help in the serialization and deserialization of data for transmission or storage.