Hi Nikesh,

We use computed fields, if the value of field is computed using some logic and depends on other fields. For example: Total in Sale order is computed from sum of line subtotal

Computed field compute its value every time we access its value instead of reading from database.

By default, a computed field is not stored to the database, and is computed on-the-fly. Adding the attribute store=True will store the field's values in the database. The advantage of a stored field is that searching on that field is done by the database itself. The disadvantage is that it requires database updates when the field must be recomputed.

For more please check Link

Hope this helps.