(Like the word techno which is often mistaken to mean all electronic music). Electronica is normally considered more intelligent than dance music. The music is about using technology to create unusual sounds, melodies and heavily processed drums (often in patterns where the same bar is never repeated requiring painstaking programming) These elements are crafted into an intricate and some times emotive piece of music. The results are usually closer ambient or experimental music than they are to dance music.
electronica is often elitist and the scene can come with some pretence. but there are some great electronica tracks out there.
Electronic fan: oh yeah? well frankie knuckles is coming to your house and is going to do a drive-by on your ass.
However, some of the people making big beat back during it's heyday are still producing this type of music, most notably The Chemical Brothers, who won the Grammy award for best electronic/dance album in 2006 (for the album "Push The Button").
Person B: It's big beat, not electronica. (Person B walks away from Person A and sighs.) Stupid media.
Examples of big beat groups: Fatboy Slim, The Chemical Brothers, The Crystal Method, The Prodigy (starting in 1997)