Accounts are grouped by primary use (for example, spending accounts are for paying ongoing personal and household expenses while brokerage accounts are for tracking investments).
Within certain limitations, it is possible to move an account from one group to another to customize the way Quicken displays your finances. For example:
If you think of your credit card as a liability, you can move it out of the Banking group and into the Property & Debt group.
You can't move a linked checking account into the Investing tab. Although a linked checking account visually appears in the Banking area, its cash balance is automatically included in the associated investment account total.