You need to ensure that the scanner you buy can read a CAN enabled network. It is a newer OBDII communication protocol. A trouble code reader that is not CAN enabled will not work on your car. The packaging of the tool should say if it is CAN enabled.
As for knowing what the codes mean there are several options. Some of the more sophisticated tools will tell you what the code means right on the screen. Some will only tell you the code. If that is the case you can look up the codes online or the codes are of course in the service manual.
Most code tools will only read Powertrain Control Module codes which are prefaced with a "P" such as P0304. This type cannot read other codes such as those prefaced with "B", "C", or "U," To read those will need a tool that costs a lot more. However, Actron makes a tool that will read "C" codes associated with brakes.
"P" codes have to do with the emission system of the car as that is what OBDII was mandated by the government to monitor.
Some tools will also let you do real time monitoring of engine systems to aid in diagnosis of problems. These types of tools will also let you read "P" codes.
All of the scan tools that I have seen will let you turn off the Check Engine light.
I hope this has helped.