criminal acts are defined by seriousness of offence:
summary offences are less serious offences, such as speeding. they are tried by magistrates.
indictable offences are more serious offences, such as rape or murder. they are tried in a crown court before a judge and jury. the sentences that can be imposed are more severe.
in the past, english law used to make a distinction between misdemeanours (minor crimes) and felonies (serious crimes). this distinction is still used in the usa.
crimes can be classified in terms of the nature of the act itself: