I'm trying to make an app using phonegap, but what I want to know is if it is possible to store information online. For example, say there is a number variable, and it is added to when a button is pushed. Could that value be saved somewhere and then a totally different device can retrieve the variable?
I looked at databases, but I couldn't really understand it. I want something that can be accessed by any device as long as It has a key or something.
Is this possible? If so, how would I do it?
This is entirely possible.
You essentially need two components: the client interface, and the server.
The client displays the results to the users, and, using your example, waits for a button to be pushed. On the push of that button, the client would send a request to the server to increment the stored value (possibly through a jQuery.post, or get, function call).
The server page, written in php for example, receives this request, and accesses a file, or more realistically a database, to increment the value.
With some Googling, this should be very doable, but post specific questions if you get stuck.