Almost every student of science is familiar with the phenomenon of waves, such as water waves ( ripples rolling across the ocean), sound waves (vibration in the air), etc. The above mentioned kinds of waves are easily observable. Electromagnetic waves are comparatively difficult to understand but not as difficult as gravitational waves. The existence of gravitational waves was disputed for a long time but is generally accepted now. What are gravitational waves? How do they propagate? And what is their energy content? These questions are addressed in this book.