Your friend is correct, but you are also correct in being careful to use the two terms interchangeably in all conversations. Voltage can be called electrical pressure or electrical tension, which seems crazy to me as the two terms sound like opposites. Unless you are an electrical engineer talking with other electrical engineers, I recommend you avoid the term electrical tension, as it will tend to confuse laymen, and you might have to (try to) explain what you mean!
A Wikipedia article is here: https://en.wikipedia.org/wiki/Voltage
Interested in Language