The last time you wrote a paper for high school or college, you were told to make sure that the beginning of the paper gave the reader sufficient warning as to the contents therein. Depending on what level you were writing, you probably heard that warning referred to as either an introduction or an abstract. Today, when you are reading papers and books, you may still notice that every well-written paper gives the reader advanced notice about what to expect. Depending on the purpose of the work, this will either be an abstract or an introduction (in fact, you are reading an introduction right now!)Definition of Abstract and Introduction
Abstract ‘“ is a short summary that is written at the beginning of a scholarly article or thesis that states the purpose of the paper and its main conclusion.
Introduction ‘“ is found at the beginning of any piece of writing that whet the reader’s appetite to read further and give a taste as to what will be in the rest of the pages. In a novel an introduction is naturally more creative than in an academic paper. Where You Will Find Abstracts and Introductions
Abstract ‘“ if you are attending a conference, you will get abstracts of all the lectures being presented. A masters and PhD thesis will begin with an abstract, as will any scholarly article that you find in a journal from sociology to medicine.
Introduction ‘“ is literally the beginning of any body of writing. Non-fiction books have introductions, as do novels. Even newspaper and magazine articles start with an introduction to draw you in. High school and undergraduate research papers have introductions that act as an abstract, but are included in the body of the work. Main Purposes of Abstracts and Introductions                                 

Abstracts ‘“ are there in many ways to save the time of their readers. The people who read academic journals generally do a lot of specialized reading and therefore want to make the most of their time. Reading a one page abstract will tell them if it is worth their while to continue to read the rest of the sixty page paper.

Introductions ‘“ are meant to excite a general reader and entice him to read on. They may be anecdotal in nature or contain a captivating quote. They can also be factual, but should be presented in such a way that the reader will want to know what happens next. Often they will combine all three elements. Summary:
1.Both abstracts and introductions are found at the beginning of a piece of written work.
2.Abstracts and introductions want to prepare the reader for reading further.
3.Abstracts accomplish point 2 by stating the purpose of the paper, whereas introductions accomplish it by drawing the reader’s interest.
4.Abstracts are generally at the beginning of scholarly work, while you will find introductions at the beginning of any kind of written work. With this in mind, an abstract is a de facto introduction.