Difference between Ubiquitous and Pervasive Computing

Ubiquitous means everywhere. Pervasive means "diffused throughout every part of." In computing terms, those seem like somewhat similar concepts. Ubiquitous computing would be everywhere, and pervasive computing would be in all parts of your life.

That might mean the difference between seeing kiosks on every street corner and finding that you could -- or need to -- use your Palm handheld to do absolutely every information-based task.

And, in fact, that's where the difference between these two types of computing lies. Pervasive computing involves devices like handhelds -- small, easy-to-use devices -- through which we'll be able to get information on anything and everything. That's the sort of thing that Web-enabled cell phones promise. Ubiquitous computing, though, eschews our having to use computers at all. Instead, it's computing in the background, with technology embedded in the things we already use. That might be a car navigation system that, by accessing satellite pictures, alerts us to a traffic jam ahead, or an oven that shuts off when our food is cooked.

Source
http://www.computerworld.com/news/2000/story/0,11280,41901,00.html