Used off-camera, the flash is triggered by using a PC cable (in M or manual mode) or via the built-in optical sensor (S1 or S2; slave modes). Used on-camera, simply mount it onto the hot shoe of a camera and use the M mode.
Why I love this flash:
Very simple to use.
Settings in 8 levels of flash intensity
Zoom setting of 24mm to 105mm
Guide number of 58 , as strong as the top end Canon or Nikon speedlites.
What this flash does not do:
There is no TTL mode
There is no built-in remote trigger
There is no high speed sync
I found that the optical sensor is not very consistent. If I use my D700 to trigger it, I have to set it to S2. While S1 also triggers the flash, only S2 will sync properly to light up the subject. On my LX7, it will trigger the flash only in S1 mode; however the flash is not in sync and the subject does not get lighted. Hence, try out before buying if you are counting on using the optical trigger.
What this flash is great for:
For beginners, this flash is very user-friendly. The interface is very basic. One can learn to control it almost rightaway. Great for anyone who is intimidated by the highly sophisticated and highly expensive proprietary top end speedlites, which can cost ten times more.
For advanced users, this flash is excellent as a second flash. For example, as a secondary light in a multi-light source setup. It is also great for use in a home studio, due to the ease of making manual adjustments.
Note: The 560-II has been superceded by the 560-III. The latter comes with built-in remote control. However, the user interface has also grown significantly more complicated. Personally, I would prefer the 560-II over the 560-III. For more sophisticated applications, I would go for top end proprietary speedlites.