QuickBooks is accounting software from Intuit for small businesses. It records invoices, expenses, and payments, and it can connect to a bank account so transactions come in for review. Payroll, time tracking, and tax filing are add-ons or higher plans, not part of every subscription.
QuickBooks Online is the browser version. Desktop versions are a different product with a different install. Plans differ by how many users can sign in and by whether inventory or billable time is included. Those differences are on Intuit’s plan comparison. A bookkeeper or an accountant can be invited to the file, which is separate from buying a second subscription.
The books are only as complete as the transactions that were categorized. Connecting a bank feed does not file a tax return by itself. Payroll, if it is needed, is the plan that says payroll is included.