Well, what you describe is the phase of a complex current. That's not inherently the same thing as the phase of an electromagnetic wave! But it's the basics of all electrical theory, so it's necessary you understand it, so you've got a good basic education there.
So, sorry to drop more theory on you:
In free space propagation, there's no current, and no voltage. There's an instantaneous magnetic field $H(t)$, and an instantaneous electrical field $E(t)$.
In vacuum or air, these two are always in phase; that's a result of Maxwell's formulas, which explain how a changing electrical field can lead to an electromagnetic wave that propagates.
So, it doesn't really matter whether you look at the E-field or the H-field of an electromagnetic wave – the other is in phase.
Thus, we simply give the whole wave a property "phase", and that's a relative quality: Two RF things have a phase $\alpha$ if one thing is, at the same instant, $\alpha$ degrees behind the other.
For example, two dipole antennas that get excited by exactly the same current have 0° phase. If instead the current feeding the antenna has to travel half a wavelength more to the antenna than to the other, that antenna has a phase of 180° (relative to the other – there's not really an "absolute phase").
Now, what does that have to do with beam forming?
Because that is a complex topic, I'll remind you of the double-slit experiment:
If you have two slits on a line, in a defined distance, from which both concentrical waves emit, then there will be points on the plane where the waves interfere. The phase of the waves, and the distance from a point to the slits, defines whether that interference is constructive or destructive.
That works with water waves in a harbour, as it does with electromagnetic waves such as laser light or radio waves.
You can influence where the constructive interference happens by
- varying the distance between the emitters (your antennas!) or by
- giving one a phase relative to the other.