affective computing!

"Distributed" or "grid" computing in general is a special type of parallel computing, it is advanced in the means of using distributed computing.

Cloud computing is better then normal grid computing as its cheaper to buy, use and maintain. Cloud computing can offer web hosting also which grid computing can not.

Cloud computing or grid computing depends on the task at hand. If you want to focus on a single enormous task, then go with grid computing. Cloud computing is more for multitasking.