“Hold the Command (⌘) key and press Tab, and the App Switcher appears, floating above all windows on your Mac screen,” Sande writes.
“As long as you continue to press the Command (⌘) key, the App Switcher stays on your screen. To move through the active apps, tap the Tab key with the Command (⌘) key still held down, and it cycles through them from left to right,” Sande writes. “When you get to the app [to which] you wish to switch… just let up on the Command (⌘) key and that app becomes active on your screen.”
Read more, including using Exposé from the App Switcher, in the full article here.