The short answer is "Yeah!" Variables are usually stored in widgets in one way or another.

The long answer is "Yeah! But there's a lot of ways this could be done depending on what you need, so it would help to narrow it down."

A field is always a good option for storing numbers and strings of text to refer to later.

Here's an example of making a user-entered name appear in an alert:

Button script:

on click do
 alert["Your name is ", namefield.text, "!"]
end

field.text is useful for referring to the simple (non-Rich Text) contents of a field in scripts.
(replace the "field" here with the name of your actual field widget!)

If you're using something like the Dialogizer module there's a helpful reference for how to do this same thing in the dialog boxes created by the module.

Or it might be handy to know how to how to refer to a widget on another card....?

Reusing the example above.... if I needed to check this same stored string of text from a different card later, I could write it like this:

alert["Your name is still ", othercardname.widgets.namefield.text, "!"] 

You can also store numbers in fields and use field.text to set them, and modify them and so on.

This is sort of just a general answer -- it might not be what you needed for your project at this exact moment. 

I'd love to make a more specific answer for you if you can narrow it down to a more specific question. :D