An Opening Balance Equity account is created the first time you enter an opening balance for a Balance Sheet account. As you enter the opening balances, QuickBooks Online records the amounts in the Opening Balance Equity account. This ensures that you have a correct balance sheet for your company, even before you have entered all your company's assets and liabilities.
An example of this is when you first add a bank account to QuickBooks Online. Since QuickBooks Online uses double entry accounting, each transaction requires at least two accounts be used. So the balance that you entered for the newly-added bank will show in two accounts, the bank and Opening Balance Equity accounts.
After you have entered all of your opening balances, you might want to move the amount in Opening Balance Equity to other accounts. Consult your accountant for advice.
If you want to learn more about Opening Equity and beginning balances, check out: How do I enter a beginning balance for an account after it has been set up?