Basically there are three different types of cases.
Summary offences are criminal offences which can only be dealt with by the Magistrates, for example driving with excess alcohol, minor assaults, criminal damage etc
Offences triable either way are ones that can be dealt with by the Magistrates Court such as assault occasioning actual bodily harm, theft or possessing controlled drugs. In these cases the Magistrates may agree to deal with you or direct that you be dealt with at the Crown Court. If the Magistrates are prepared to deal with the case, then you have a "right of election" to decide whether the case is dealt with summarily by the Magistrates or committed to Crown Court for trial by jury.
Indictable only cases. These are cases that can only tried "on indictment" at the Crown Court before a judge and jury such as any conspiracy, robbery, manslaughter or murder.