A one2many field represents a one-to-many relationship between two models in Odoo. One record in the current model can be related to multiple records in another model.

class MainModels(models.Model):
    _name = 'main.models'

    the_field = fields.One2many("comodels.of.main", "model_id")

class ComodelsOfMain(models.Model):
    _name = 'comodels.of.main'

    model_id = fields.Many2one('main.models')

Key points about one2many fields:

• They require a corresponding many2one field in the related model
• The field itself doesn't store any data - it's a virtual relationship based on the many2one field in the related model
• They're commonly used for showing related records in views, especially form views where you can see and edit child records
• The field name typically ends with '_ids' by convention
• In the UI, they're often displayed as editable lists or kanban views embedded within a form

Common use cases include:

• Companies having multiple employees
• Sales orders having multiple order lines
• Products having multiple variants
• Invoices having multiple invoice lines