Supernodes with Constant Current & Voltage Sources: Voltage = Current
This is a classic circuit theory example. The book you are working out of is probably a good one. This chapter is going to be rather math heavy with many systems of equations. Circuit theory as a whole is very math heavy, so be prepared for that.
In your description you call that a dependent current source, but have drawn a dependent voltage source. Based on your explanation it seems like that stems from your voltage/current confusion.
In this particular case the dependent voltage source is dependent on a current somewhere else in the circuit. This doesn't mean that current = voltage. It means that in this case the voltage changes based on the current through a different part of the circuit. Its just an exercise in practicing whatever circuit analysis concept they are trying to teach.
((Changing the problem)) They could have just as easily said that the dependent voltage source = 5V2. Now its a voltage source dependent on a voltage. All they are doing is getting you to practice with all the different elements in circuits.
Later on in your studies you will come across bjt's and other active circuit components that are modeled with dependent sources.

http://fourier.eng.hmc.edu/e84/lectures/ch4/node8.html