Variable values are shown within grey overlays in the source code view. These overlays are always displayed straight above corresponding instructions.
To see all variables in the current scope, open Variables window through RevDeBug Menu (RevDeBug > Variables).
Here you can see all variables with their current and previous values.
Click on icon of two arrows to get a list of all the recorded values of a single variable.
Click two times on one of these values, to jump to the state (i.e. exact moment in time) it was set or read.
Go to the next chapter, to learn how to follow threads.