In accounting system general ledger represents a group of such accounts that are not maintained under any specific or special ledger. For example capital account.
In short, any account that is not grouped under sales ledger, purchase ledger, cash book is maintained under general ledger. This leave us with accounts that are related to asset, liabilities, incomes, expenses, equity and few others that are necessary for preparation of complete set of financial statements. Due to this fact, general ledger usually contain large number of accounts.