What is meant by adjustment entry?

What is meant by adjustment entry?
An adjustment is usually an entry made near the end of an accounting cycle (often during the trial balance stage) to bring an account into balance. For instance, the "books" may show a certain quantity on hand -say 1000 units- of supplie, but when you do a physical count you discover there are only 900 units on hand. At this point you will have to make an adjusting entry to the supplies expense account (a credit balance account-the supplies account has a debit balance) of 100 to offset the supplies account and bring the account in balance: Or you can just credit the difference directly into the supplies account:
Debit Credit Balance
Supplies- 1000 (100) 900