Question

what is the use of validation text property of a field

Answer 1

You are most probably talking about MS access.
When a value is entered, its validity is first checked.If it is invalid (that is,not conforming to the validation rule) then the validation text is displayed.
Its use is that it may tell a new user what type of value is to be input, so that he/she may not have knowledge about knowing exactly what is the validation rule, which is making any value invalid, and may not know the procedure to gain this knowledge.

Answer 2

When the data entered in a field does not confirm to the validation rule that is specified, an error message is displayed on the screen that informs the user what is wrong. Validation text is used to display custom error message instead of default error message.  \
PLZ PLZ I REQUEST YOU SO MUCH T0 MARK MY ANS AS BRAINLIEST