The name 'Carthusian' is derived from Chartreuse, a French valley which was where St Bruno built his first hermitage. The word 'Charterhouse', which is the name for a Carthusian monastery, is derived from the same source. Today, the monastery of the Grande Chartreuse is still the mother abbey of the order.
Carthusians have no active ministry because they are strictly cloistered. Monks or nuns spend most of their time alone in their cells, although they do come together for certain prayers and for Sunday dinner. Meanwhile, lay brothers tend to the material needs of the abbey. Today Carthusians live very much as they originally did, without any laxing of their rule and thus never having needed any kind of reform.
The best preserved remains of a medieval Charterhouse in the UK are at Mount Grace Priory near Osmotherley, North Yorkshire. One of the cells has been reconstructed to illustrate how different the lay-out is to monasteries of most other Christian orders, which are normally designed with communal living in mind. The Carthusian monk (or nun) lives a solitary life in a 'cell' (actually more like a small house), which typically consists of three small rooms on the ground floor - bedroom, study, and shrine - and a work area in the upstairs loft. Each cell has its own water supply and lavatory, and a tiny private garden planted with herbs and flowers. The garden would normally be cultivated by the monk as part of his daily duties.
Today, there are 24 Charterhouses around the world, five of which are for nuns; altogether, there are around 370 monks and 75 nuns. Most of these Charterhouses are in Europe - including one in Sussex, England - but there are also a couple in South America and even one in the USA, in Vermont.
The London Charterhouse gave its name to a square and two streets in the City of London, as well as to the Charterhouse public school (UK sense) which used part of its site before moving out to Surrey.