The emphasis is on understanding concepts. I think that nearly everybody agrees that this should be the primary goal of calculus instruction.
In writing the eighth edition my premise has been that it is possible to achieve conceptual understanding and still retain the best traditions of traditional calculus. The book contains elements of reform, but within the context of a traditional curriculum.
I recommend that you keep this book for reference purposes after you finish the course. Because you will likely forget some of the specific details of calculus, the book will serve as a useful reminder when you need to use calculus in subsequent courses. And, because this book contains more material than can be covered in any one course, it can also serve as a valuable resource for a working scientist or engineer. (Source: Calculus: Early Transcendentals, 8th Edition; James Stewart; Cengage Learning ; Preface: Pages 13-25)