Jib

You have not given the full form of b/w, I assume it as a gantry crane or EOT crane which is moving between two rails and loads to be handled should be between these two rails. So, its simply supported and having long travel, cross travel & hoisting mechanisms.

Jib crane is a cantilever crane, supported only on one side on a pivot, generally on a column at certain hight. It has cross travel from pivot (fulcrum) to the free end on the beam and angular travel of the beam w.r.t. fulcrum besides hoisting.

If the meaning of b/w is boom on wheel, then the difference would be mobile and static.

What is b/w? Please don't tell me it's an "abbreviation" of between!

This should help. The boom is attached to the crane, the jib is attached to the other end of the boom. However, some people use the terms differently and cause confusion, context is most important.

now tell him about the davit