Dangerous driving is a more serious offence than careless driving and requires a greater degree of fault or neglect. The offence can be committed based on the state of your vehicle as well as the quality of your driving or riding.
To prove dangerous driving it has to be shown that the standard of your driving fell well below that of the reasonably competent driver. The Highway Code is indicative of the standard of a reasonably competent driver that should be applied, but if your driving or riding put someone else at risk the offence is likely to have been committed. The same applies if you were not paying attention to what you were doing, such as when using your mobile phone.