What is difficult is that there are no hard and fast rules. I've seen house labeled electronica and vice versa. It all depends on the background of the person doing the labeling.
There are some basics that can be described:
House: Has a strong tie to hip hop. The music has a hip hop base, but these songs can also be melodic. House music almost always has standard vocals: not rap, not etherial, and frequently in something resembling sentence form.
Try the C2 Mix on this page:
http://www.djmr.com/scripts/category.cgi?type=store&category=100_H_Vocal
Deep House: Similar to house, but the hip hop sound has been tempered with jazz and soul. Beautiful stuff here.
Try this:
http://www.djmr.com/1/276367.mp3
Ambient: Will usually put my wife to sleep. Sounds and phrases tend to fade into each other. Vocals are usually non-existent unless used musically. Song lengths typically exceed 6 minutes. If you see a club with a "chill-out room," this is what is played in there. This always reminds me of the background music in movies.
This is an excellent example:
http://www.shopsonic.com/preview/128/1114/Azure_Day.mp3
Trance: This is classic techno/electronica with an spacey, hypnotic quality to it.
Try this. You can actually hear the shift from Ambient to Trance:
http://dw.com.com/redir?&destUrl=http://music-files.download.com/mp3
Industrial: Has a heavy metal background with a driving beat. Instrumentation commonly, but not necessarily, includes things that be at home in a factory. If it sounds like metal, thrash, or goth with a dance beat, it's probably Industrial.
This certainly qualifies:
http://www.internetdj.com/artists.php?op=stream&song=7771
Drum & Bass: Also called Tribal. The beat is king. If you hear something that sounds like a tribesman on PCP, this is probably it. I have also heard it called A**hole Techno because it does seem to attract those people. As a backlash, you will find stuff called Intelligent Drum & Bass.
Electronica: This is very close to typical Top-40 dance music without all of the bubblegum. Instrumentation is almost exclusively synthesized.
Trip Hop: Basically a fusion of House and Ambient. The underlaying beat is usually House with an Ambient sound layered on top.
Acid Jazz: This is Ambient with a Jazz mix and is very similar to Trip Hop, but has a much more psychadelic/spacey feel.
Try this:
http://www.peoplesound.com/music/play_stream.cfm?ID1=46839
Techno: This is not a type of music unto itself and frequently emcompassed all of the above types, but is sometimes used to describe Electronica.
That's all I have time for today....