What is Data Modeling?
Data modeling is the process of deciding how data is structured: which tables exist, what each row represents and how the tables connect.
Data Modeling explained
A model turns a messy business into something a database can hold. Modelers decide the entities (customers, orders, products), their attributes and the relationships between them, and document what each field means.
For analytics, modeling also fixes the definitions people argue about: what counts as an active customer, which date an order belongs to, how refunds are treated. A clear model is what makes two reports agree.
Example
Deciding that 'one row in the orders table is one checkout, and order_items holds its lines' is a modeling decision that every later query depends on.