Much of the data in the PKI world is stored in ASN.1 so a basic understanding is necessary. ASN.1 is a way to describe data by starting from primitive types and building up to more complex types. Do you remember Backus-Naur Form? What about writing XML schemas in XSD? It's the same concept.
Let's say we have a Widget. Every Widget has a model name, a serial number, and some inspection information with the name of the inspector and the dates of the inspections. Our Widget then looks like this in ASN.1:
Widget ::= SEQUENCE {
model IA5String,
serialNumber INTEGER,