Hi Gaurav,
An inspection is a "structured review of the work being performed by the contractor" (PMBOK® Guide page 498). So for example on construction projects, walkthroughs are commonly used to review the progress of the construction process.
An audit (as it relates to the procurement process) is a "structured review of the procurement process" (PMBOK® Guide page 498). So for example conducting a review of the contract to ensure both sides are meeting their obligations.
It might help to think of an inspection as related to the deliverables and an audit as related to processes.