Description:
Relational Fields provide the option to link the data of one model with the data of another model.
In Odoo, relational field types are One2many, Many2one, Many2many.
An One2many field is a one-way direction of selecting multiple records from a table.
For example, a Sales Order can contain multiple Sales Order Lines, which also contain multiple fields of information.
A Many2one field is a one-way direction of selecting one record from a table.
For example, you can have many product categories, but each product can only belong to one category.
A Many2many field is a two-way direction of selecting records from a table.
For example, multiple tags can be added to a lead’s form.