How to switch between tabs in Opera?
If you are looking for keyboard shortcuts, then Ctrl + Tab will move to the next tab, and Ctrl + Shift + Tab will move to the previous tab.
Under Preferences -> Advanced -> Shortcuts you can also enable single key shortcuts. You can then use 1 and 2 on your keyboard to cycle forward and backward through tabs.
You can also use mouse gestures: Cycle through open tabs -> Hold right button, roll mouse wheel