They call a table definition - that defines a table at both the SQL level, and at the domain level - a DocType (see: https://docs.frappe.io/framework/user/en/basics/doctypes). When you declare a DocType you immediately get a working table, foreign keys transformed into combo boxes for lookups, forms, and a whole set of conveniences that are common to ERP-like applications.
Before seeing ERPNext I would've thought that such a declarative approach would fail to satisfy the critical remaining 20% of most requirements, but they've built around it in a way that has enabled them to ship a complex ERP system that thousands of businesses of different shapes use. I think it is one of those gems that are not in popular conscience among software engineers, compared to regular frameworks (but very much so in business-ERP adjacent circles), and is worth learning from.