I am a student too so someone may be along with a better answer!!
You would open a suspense account if there are errors in the trail balance that cause it to not match (the credit and debit sides). You then put the difference into the suspense account and then begin to investigate the errors, usually tracking back to your last trial balance and looking through the ledgers. As you find where the errors are you can begin to make the amendments to the suspense account and the accounts in the ledger. You will eventually clear your suspense accounts and the corrections in the ledger accounts will mean that the trail balace will match.
There are other errors that can be in the GL that do not effect the blaances on the trial balance, these errors (if found!!) would need amending but no suspense account.
Who are you studying with? Could your tutor not send you some additional information to support you through this?
Hope that helps?