Cloud computing is rapidly grown, highly promising future for both IT Industry and internet users. Cloud computing requires no upfront infrastructure investment, since the developer will use an existing hardware. Cloud computing have efficient resource allocation and supports pay-as-you-go, which means developers pay only the resources they use. Cloud computing is highly available, scalable and energy efficient. Pay-as-you-go is the pricing model. This means developer pays as they allocate resources from the vendor. Unfortunately it is not flawless; security, confidentiality and vendor lock-in are main challenges.