Push is a newbie offensive skill. Most players that get it will soon get access to something better, but it is far better than nothing. Rangers have a guild task that requires using push, and even have access to a guild boon to make it useful for disrupting monster skills. Still, this is fundamentally a newbie skill and not used much past the lower levels.

The ingame help reads:

Skill duration: 2.
Type of skill : offensive skill.
Party rows    : 1st.
Affecting stats: Str.
It uses 11 endurance points.
While fighting an opponent in a melee, there
are many ways a skilled attack can gain an advantage.
One of the simplest forms of fighting taught, is to
step into the target and give him a solid shove.
While the damage is light, this skill is easily mastered
and the basis for many fighting styles. The stronger
the fighter, the harder he can push his opponent.