The personal budget is the notional amount of money that would be needed to cover the cost of making the special educational provision specified in the EHC plan. You cannot have a personal budget unless you have an EHC plan.
Normally, the LA will do this by providing the necessary funding to the school or college attended by the child or young person, so they can deliver the educational support needed. However, the LA to can consider making a payment to the parent or young person, so that they can arrange the provision themselves. This is called a direct payment.