.
They 'bridge' the gap between a compact and an SLR.
Personally I don't see the point of them as they are very nearly the size of some of the smaller SLR cameras.
They do however usually have quite a long zoom on them as standard so you don't have to carry a bag of lenses with you. – However. The lens on them is usually quite slow (high f stop) and so at longer focal lengths will require the use of a tripod for best results. You cannot have it all.! Image stabilisation on them will help a bit I suppose but IMHO they are a marketing ploy that works well for them in sales.
Nick