An abstract condenses a longer piece of writing. It is a summary of that piece of writing, and should be clear and concise.
An abstract, by its very nature, needs to be short. It should tell a reader what it is you want to do and why – your objectives and purpose. It should than describe how you did it -your methodology, and concisely explain what you found – your results and conclusions. The abstract should stand on its own, able to be read and understood separately from the piece of work and should show a reader quickly if the whole work is relevant. The abstract should include key words. It must indicate the thoroughness of the work but should not include references, abbreviations or citations. It should be set out to follow chronologically the order of the work, connecting the information. It is important that it summarizes the information of the whole, and does not include any new information. It is a good idea to write the abstract once the original work is completed.
The purpose of an introduction is to lead the reader in. The introduction should clearly identify the topic of the work. It should define the topic. It should inform the reader of the areas covered, of what is included and what is left out. It should identify the approach taken by the author and give an outline of the topic.