There are three major types of cloud computing, they include; IaaS (Infrastructure as a Service), PaaS (Platform as a Service) and SaaS (Software as a Service).
Gmail is a SaaS cloud computing service. When you use Gmail, you are not hosting your own email server. Google Cloud Platform host gmail. Google keep gmail up and running, track and report accurate billing and facilitate a secure environment data. Google owns the content on gmail.
Google is a cloud-computing service. It is hosting the service when you use gmail. You are not hosting your own. Therefore the content belongs to Google. Gmail is a simple form of software as you service (SAAS) cloud computing service. It can fail, and has done several times, prompting the media to pronounce SAAS on its death throes.
But this hasn't happened yet. the reason? Well, one important one is that it is a hassle and expense to provide your own network. Another is that Google is so big. Even huge companies that do have their own network have frequent system failures or down-time for their network.