The book is intended to act as a foundational textbook for physics undergraduate and graduate students. It gives a complete, cogent explanation of the foundations of electromagnetic theory. The book's main goal is to help the reader achieve a satisfactory intuitive understanding of the subject, help him realise how important and practical it is, and inspire him to become more skilled in using it. The book fills the gap between very basic introductions to the topic and highly mathematical publications. A few new features have been added to the fourth edition of this book.