It is just a continuity tester, really - it shows a light for each pin in each type of cable - but not all at the same time. For example you have to turn the (admittedly very solid high quality) knob and it will show you each pin.
What it doesn't do is latch on any warning for an intermittent fault, eg if you wiggle the cable and it stops working, it will just go back on again - this will only show you a yes-or-no is it conducting electricity. There is no measurements of resistivity or noise or anything else useful.
This is the first cable tester I have used but it doesn't really test anything, it just just what any standard multimeter would do but without the sockets.
Admittedly the sockets make the task of checking many cables at once much quicker!
If you're a neurotic gigging guitarist like me, you'll be familiar with the fear of dodgy leads degrading your sound. I've found this device to be very useful. It's not something that you'll be using all the time, but it's nice to check your cables now and again to put your mind at rest. It's so easy to use that the instructions aren't even necessary and it will test most types of cables. Recommended for anyone serious about maintaining high quality performance sound.