Instead of making multiple payments to multiple lenders on your student loans, you make one payment to one lender.
A consolidated loan is a new loan that will give you a new due date, thus giving you more time to pay off your loan.
You will receive a new 3-year limit on certain deferments and forbearances.
If you opt for an extended repayment plan, you will pay more interest over the life of the loan.
Because your loan is locked in at a fixed rate, you will not be able to obtain a lower rate.
If you consolidate your loan during a grace period, you will lose the remainder of your grace period.