$lookup

A `$lookup` is a feature used in databases to combine information from two different collections or tables. Think of it like cross-referencing two lists: one list might contain customer details, and the other might have orders. `$lookup` lets you join these lists based on a common key, such as customer ID, so you can see all orders alongside customer info in a single view. It simplifies gathering related data without manually searching or merging outside the database, enabling more efficient and organized data analysis.