The offence of careless driving comprises both careless driving and inconsiderate driving. The offence was updated in 2007 partly as a result in changes in the Highway Code.
The offence is that you failed to show the standard of a careful and competent driver in the circumstances and that you knew of or should reasonably have known of those circumstances. Inconsiderate driving requires that someone should have ben actually inconvenienced by your driving.
The penalty for careless driving is a fine of up to £5000, 3-9 points on your licence and a discretionary disqualification.
Offences involving distracting behaviour on the part of the driver are usually prosecuted for careless driving eg eating and drinking, smoking or changing a cd in a cd player would be examples of careless driving.