A volt is a unit of electromagnetic potential. It if the electrical equivalent of a Newton (N).
In the physical world, potential kinetic energy increases as a function of mass and distance. (Heavier things and things dropped from higher collide with more force.)
In the electrical world, electromagnetic potential increases as a function of charge and the distance. (Imagine filling a bag with sand. Each grain is a single charge carrier, as you collect more, the bag gets heavier and the potential energy increases.)
Charge is two dimensional characteristic — it has a positive and negative. Direct current fixes which which conductor is positive and which is negative while alternating is constantly going between the poles.
Direct current always has the save value for the voltage whereas alternating current only has a constantly cycling instantaneous value for the charge (and thus the voltage).
So, alternating and direct volts are the same unit in the way that a pound of granite and a pound of water are the same unit even though the quantities being measured are vastly different in fluidity.