What is a Letter Of Introduction?

The letter of introduction, along with the visiting card, was an important part of polite social interaction in the 18th and 19th centuries. It remains important in formal situations, such as an ambassador presenting his or her credentials, and in certain business circles.

Why write a letter of introduction?

The primary purpose of an introduction letter, or letter of introduction, is to introduce yourself and/or your business (or another person or business) to another party. Introduction letters are important business letters because they are usually the first point of contact when you are trying to develop or grow your business.

Sources: https://en.wikipedia.org/wiki/Letter_of_introduction, http://www.writinghelp-central.com/introduction-letter-samples.html