The informal review - is generally a one-on-one meeting between the producer of a work product and a peer or co-worker, and is initiated as a request for input regarding a particular artifact or problem.
There is no agenda, no preparation time, and results are not formally reported. These reviews occur on an as needed basis throughout each phase of a project.
The semiformal (or walkthrough) review - is facilitated by the producer of the material being reviewed (e.g., documentation or code). The participants are led through the material in one of two formats: the presentation is made without interruptions and comments are given at the end, or comments are made throughout.
In either case, the issues raised are captured and published in a report distributed to the participants. Possible solutions for uncovered defects are typically not discussed during the review. Semiformal reviews should occur multiple times during a phase for segments or “packages” of work.