A one-to-many relationship means one parent record can have many related records, while each related record belongs to one parent. A typical example is a Post that has many Comments, where each comment stores a post_id foreign key.

In Eloquent, the parent model usually defines hasMany and the child model defines belongsTo. The relationship lets code retrieve related records, constrain them, create them through the parent, and eager load them efficiently when rendering a list of parents.