I started to write out an explanation, then decided this was easier. Check
out http://en.wikipedia.org/wiki/French_drain

Adelle

First of all let me state that french drains are not naughty!!!   Let
me try to explain it terms that probably only I understand (g)

Ground water used to bubble up through basement floor, lifting the
cement to get through.  Looked like a spring sometimes.  French drains
were two trenches about four to five feet deep from the middle of the
basement to the foundation walls and beyond.  They were lined with
crushed stone and then that white pipe with the holes in it was layed
down and trenches were covered up and cemented over.

The idea is that water will now go in the trench and drain outside of
the foundation. I still have the sump pump in a hole in the floor on the
other side of the basement too.  All of this works just fine until a
pipe breaks when you are not at home.

Ann