Alt-Tab

Alt-Tab is the simplest and oldest multitasking user interface in Windows, and it works as it did in Windows 10 and previous Windows versions: type ALT + TAB, but keep holding the ALT key down to display thumbnails of all of the available apps and other windows to which you can switch the focus.

Use Alt-Tab to switch between open windows
When you open Alt-Tab, the thumbnail for the next window in the z-order---the list of available apps and other windows, listed in the order in which they were most recently accessed--is selected. (Put another way, the window you most recently accessed is selected.) So you can quickly switch to this window by letting go of the ALT key. Alt-Tab closes when you do so.

Indeed, you can quickly toggle between the two most-recently-accessed windows by repeatedly typing ALT + TAB.

To select another window, type ALT + TAB, keep the ALT key held down, and repeatedly tap the TAB key. As you do so, the selection will change. When the window you want is selected, release the ALT key.
Determine whether Microsoft Edge tabs appear in Alt-Tab
Alt-Tab seems simple enough, but there is one wrinkle that's unique to Windows 11 (and Windows 10): in addition to working with any open apps and other windows, Alt-Tab is configured by default to let you access the three most recently-accessed Microsoft Edge tabs as well. So if you use Microsoft Edge, you will see Edge tabs in Alt-Tab as well.

This may be desirable. But you can configure this feature to work the way you want, including excluding Microsoft Edge from Alt-Tab.

To do so, open Settings (WINKEY + I) and navigate to System > Multitasking. Here, you will see an Alt+Tab setting with four possible configurations.

The following choices are available:

Open windows and all tabs in Microsoft Edge
Open windows and 5 most recent tabs in Microsoft Edge
Open windows and 3 most recent tabs in Microsoft Edge (the default)
Open windows only