This works as it should, with minimal issues.
First thing to note is that you'll need a HDMI cable to be able to connect this to your TV. This adapter has a micro-USB connector to attach to your Nexus 7 (or other slimport device) to on one end along with a "normal" USB connector. This allows you to connect it to a power supply (eg your charger or laptop) to charge your device as you watch it on your TV.
The other end is a HDMI out, you attach the HDMI cable to the TV here.
I did find one weird issue with this; If you connect everything up before your TV is on the correct HDMI channel, the picture shows on your TV but the sound still comes out of the tablet. To remedy this simply unplug the micro USB connector then plug it in again. This seems to sort the issue out.