An abstract is a brief statement which outlines the report in full; what was done, achieved, decided and concluded.
The introduction is a section which states your aims and some required background knowledge. An introduction will also outline the body of the report (where you state what you will do).
Don't confuse the introduction with the abstract or summary; they are very different. Writers often confuse the main purpose behind writing an introduction and an abstract. The common misconception is that one is simply a smaller version of the other (that the introduction is a rewritten, chopped-up version of the abstract). However, this is not the case.

The Abstract
Most reports need an abstract, but they are generally more important for technical reports or scientific documents.

An abstract is a succinct passage which provides a brief outline on what was achieved/decided/concluded in your report.
An abstract is placed on a separate page before the contents page.
An abstract can be written last so that every bit of necessary detail is taken from the finished report.
An abstract is one part of a report that will certainly be read by a client/assessor/manager. The rest of the report is read if more detail is required.
An abstract is about half a page in length. Sometimes a word limit is given. This can range from 50-300 words.

 

 

The Conclusion
The conclusion (along with the introduction and abstract) is generally the section most read by clients. If you can conclude your work /findings well, you facilitate your client’s understanding of your work’s significance, your achievements and whether your aims have been successful or not. Even in the face of failure, e.g. your experiments do not work, a proper conclusion would demonstrate an understanding of what you achieved. Here is how to do that: