Paul Coehlo's The Alchemist deals with several themes, including the nature of desire, coming of age, seeking your life's purpose, recognizing and attaining your dreams, and paying attention to the beauty and lessons you encounter on your journey. Below are a series of fundamental lessons that Santiago learns through the five main parts of his journey to self-fulfillment and understanding.
The protagonist, introduced to the reader simply as a young boy on the cusp of adulthood tending sheep in the Spanish country side, encounters a mystical figure who encourages him to take his first step into the wide world beyond his familiar, recognizable homeland. Thus the first lesson Santiago learns in the first part of the book is to recognize the inherent calling that makes you, you and to embark on a journey of discovery to seek after that calling (part one).
After Santiago embarks on his journey to seek a "treasure" hidden in The Great Pyramids, he begins to encounter difficulties and the struggle to stay your course in the face of challenges and complexity. He learns through daily living with a merchant in Morocco that everyone in life has a deep purpose and it's up to each of us to pursue it and not stay stagnant. Santiago sees a reflection of this potential future in the crystal merchant he takes up shop with, and he learns to avoid being lost in the minutiae of life's ups-and-downs, finally recommitting to his quest (part two).
Santiago begins the long journey across the wide desert of the Sahara on his way to Egypt, and now he has built up his skill for interpreting the signs in the world that can help or harm you. His time in the desert among the nomadic people teaches him to live without fear and recognize how the world teaches you to achieve your life's purpose (part three).
In his journey across the desert, Santiago also learns to set aside all else but the goal of your desire, understanding that everything works out in its own time (part four).
And finally, at the completion of his journey Santiago learns that you must always apply everything you've learned to overcoming the greater and greater difficulties that life sends your way to test your knowledge, resolve and dedication to achieving your purpose (part five).