My 92model civic does not pick sometimes on motion,it will be humming.we have changed airflowmeter,n fuel distributor.pls any help?

What exactly is:

"pick sometimes on motion".
I might be a gearhead but this escapes me!!

Ooookaaaay... It may be "humming" because it doesn't know the words..
A little more info may be needed here, please...
First, why was the airflowmeter,n fuel distributor changed?