A bell tower in which bellringing takes place will contain anything from three to twelve bells; towers with six or eight bells are most common. The bell highest in pitch is called the treble, and the bell lowest in pitch is called the tenor. For convenience, the bells are numbered, with the treble being number 1. The bells are tuned to a Major scale, with the tenor bell being the key, or base, note of the scale.
When bellringing, each person controls one bell via a rope. The rope has fabric over part of it, called the Sally. The rope goes through a hole in the ceiling into the chamber containing the bells. The bells are mounted on wooden wheels around which the rope is wrapped. By pulling the rope, the ringer causes the bell to swing back and forwards through a 360 degree circle. Ringing doesn't just involve pulling the rope - it also involves knowing when to let go of the rope as well - this is a skilled art in which people can get injured!
The simplest form of bellringing is ringing Rounds, which means ringing the bells in the order 1, 2, 3, ... (i.e. in increasing number order all the way down to the tenor bell).
The main style of English-style bellringing is "change-ringing", also known as "method ringing" and "scientific".
Change-ringing involves permutation of the order of the bells on each stroke according to a certain algorithm, which can be expressed as a place notation (wherein the bells which strike in the same position in the following sequence are listed and no others).