What is the difference between odb code reader and odb scanner?

My definition between the two, A code reader just reads the code and a scantool gives you live data on parameters and actuators

a code reader is just that it reads codes a scanner will read codes and will read readyness status of monitors. A code reader just pulls codes. a scanner pulls codes, stores freeze frame data and you can view live sensor data. the engine light may not be on but there may still be a codes stored in the computer. the code reader can still be used to check for codes that don't turn the light on. In a word it is Same as scons and scones if you ask me

You just have to make sure that your car will support live data on the unit you end up purchasing, some manufacturers block live data read out with out a factory scanner.