Cloud Computing is the act of deporting all or a part of one's Information Technology on remote servers.
We distinguish three big models in Cloud Computing : the IAAS, the PAAS and the SAAS.
IAAS (Infrastructure as a service) is the first model :
PAAS (Platform as a service) is the second model :
SAAS (Software as a service) is the third model ; it consists of using a supplier's applications with a simple web browser. The Cloud supplier maintains : the applications, the runtimes, the SOA integration, the databases, the server network, the virtualisation, the server hardware, storage and the networks.