I'm just curious I hear this words very often?

A man who takes initiative and control in any situation, especially relationships. The term stems from the wolf animal species. However, I really like wolves because not only is there an Alpha male in the pack, but also an Alpha female. Instead of it being a monarchy, the couple run the pack together. Very cool, very romantic.

a postal box full of alpha bits

The term is social masturbation.

Alpha males are the strongest or prettiest males in the animal kingdom.
They possess the genetic traits or physical displays which tells the females it is wise to mate with this male.
Alpha males also tend to mate with multiple females in the herd.

Human males who socially think they are or want to be alpha males usually have bloated egos or excessive self-esteem. They are most likely to adopt narcissistic psychopathic or sociopathic behaviors. They are also likely to be less sensitive and/or aggressive towards females.

Truly strong men have no need to emphasize their strength to the female population. They need no labels. Women can 'see' them quite clearly.

I think were we go wrong here is with the comparison with animals. We are not animals. Some still think that, it is not true nor correct. The one about the wolves was almost correct, as it was meant to underwrite the alpha male being able to live in balance with his alpha female, with whom he mates for life.

I think what nowadays is referred to as an alpha male is the one who is:
- empowered,
- confident, confidence from the inside out, not dependent on external things for this
- doesn't need to pretend to be more or different than he is
- isn't driven by ego
- Doesn't need to get attention
- a strong aura that can be sensed when he enters a room without calling attention to himself
- Can listen
- Can express his own feelings
- He is empowered, introspective, grows and learns
- above all he respects others
- can handle & is ready for an interdependent romantic relationship
- doesn't need to be right (=ego)
- natural leader, and these are often the ones you wouldn't expect to be one

In actual fact it is more like what is called "Sigma male".

in a 3some?

An alpha male is pretty much the exact opposite of the males being produced nowadays.

Studies have shown a dramatic decrease in men's testosterone levels since the 1980's.

In other words, for today's millenial and younger "men", yes your fathers and grandfathers were twice the men you guys are today.

It's all them skinny jeans, crushing their nuts