Abstract Syntax Notation version 1 = ASN.1. Since there is no version 2, ASN is the typical abbreviation here.
In the time before internet there was the 7 layer ISO model and a bunch of PTOs (mostly government postal an telegraphy organizations worried by this new technology) that wanted to dominate the identity layer of the internet. The result was a series of CCITT (now ITU-T) committees establish to translate the telephone industry white pages into the identity of every entity on the internet. This expanded to include X.400 series standards on electronic mail which went beyond that to create a security system base on ASN.1 X.500 series standards. The only legacy of that is the use of Distinguished Names in email directories, like Microsoft Outlook.
Abstract Syntax Notation One (ASN.1), which is defined in CCITT Recommendation X.208, is a way to specify abstract objects that will be serially transmitted. The set of ASN.1 rules for representing such objects as strings of ones and zeros is called the Distinguished Encoding Rules (DER), and is defined in CCITT Recommendation X.509, Section 8.7. These encoding methods are currently used to create the TLS certificates that are used to establish secure interchanges using HTTPS.
Convert it all to json format so we don't need to spend so much effort understanding an syntax that was unnecessarily complex.