DBIx::Class is an ORM, an Object Relational Mapper. It tries to bridge the conceptual difference between the representation of the data in a Relational database where it is stored in tables, and the application where the data is stored in Objects.
In order to understand it you'll have to understand both objects and relational databases, though you don't necessarily need to know SQL, the language that is usually used to talk to relational databases. One of the key features of every ORM, and thus DBIC is that, it eliminates the need to use SQL. At least in the common cases.