First and foremost, there is no "cloud". There is no ethereal
place in the sky that holds your computer information.
The computer information (data files), is on someone's computer. Simply said, if you have a Gmail or Yahoo email account and you start up your computer and with your browser, (Edge, Firefox, Chrome or whatever) you go to your email page at Yahoo to view your emails, you are looking at the reserved space assigned to you on Yahoo's computers (servers as they like to call them). This scenario holds true for Gmail, Hotmail, etc. You are, in effect, "in the cloud."
As long as the server Inbox contains something, it is in the cloud --- not on your computer. This is true for info in your "Sent" box or "Trash", if you don't empty it.
If you use an Email "client" (a separate application, like Mozilla Thunderbird) then it will download your email files and place them on your computer. Your info will no longer be in the cloud. The cloud problem arises, and be very aware of this, after six months. The information is open for scrutiny without a warrant. If you send or receive sensitive information, make sure it is encrypted.
A program like Dropbox will purposely upload your files into their
servers and store them for you. They are considered in the cloud. They
will tell you that your info is secure. And it is, in the sense that
access to your files is prevented by
your password. But once surveillance is there, they are readable
as easily as when they are on your computer. This is why we recommend
you encrypt them first with Away RJN Cryptography because the six
month limit applies here as well.
From Bruce Schneier Blog May 23, 2012; "The meta-issue is pretty simple. If you expect a cloud provider to do anything more interesting than simply store your files for you and give them back to you at a later date, they are going to have access to the plaintext. For most people -- Gmail users, Google Docs users, Flickr users, and so on -- that's fine. For some people, it isn't. Those people should probably encrypt their files themselves before sending them into the cloud."