Human population growth and development activities, growing at a rapid pace today, have increased the energy demands. Global concerns over above facts linked to fossil fuel consumption have increased the pressure to generate power from renewable sources. Owing to present day's energy crisis, growing environmental concern and escalating cost of fossil fuels, we ought to take every effort to supplement our energy base with renewable sources. Without any doubt, renewable energy, especially solar, wind and wave energy will play an important role in 21st century. Main disadvantage of wave power is its largely random variability in several time-scales, from wave to wave, with sea state, and from season to season. Present situation shows a wide variety of wave energy systems, at several stages of development, competing against each other, without it being clear which types will be final winners. In last few years, interest in wave energy utilization has been growing rapidly in all over the world. High costs of constructing, deploying, maintaining and testing large prototypes under harsh environmental conditions, has hindered the development of wave energy systems. In this paper, some wave parameters have been discussed that are related to transport, generation and variability of wave energy in the sea. Wave Energy Converters (WECs) are classified into different groups. In order to develop a commercial WEC is not a straightforward task. Many inventions still have to be made, and many challenging problems need to be solved.