An introductory remark, talk, or part of a book gives a small amount of general information about a particular subject, often before a more detailed explanation.
双语例句
例：
an introductory course in religion and theology.
一门宗教和神学的入门课程。
2.?试销的
An introductory offer or price on a new product is something such as a free gift or a low price that is meant to attract new customers.