Two or more planetary energies are combined into one powerful dynamics.

When planets are close (0-5 degrees apart) act as a unity.
The conjunction is a concentrated value of energy of that sign, together with a merged functions of the planets involved.

The Ancient Greek considered conjunction more that an aspect. They saw it as a supreme importance as the energies of this fusion merge a new entity together that influence a persons character. All conjunctions involved personal planets (Sun, Moon, Mercury, Venus and mars) bring more important.

Moon-Saturn conjunction puts a cup on emotions, giving Saturn restrictive influence. The only fear a person might have hard time to overcome is a fear of loneliness.
Any conjunctions of other planets to Saturn will put restrictions and forbidden influences.

Any conjunctions to the Sun gives a voice to a planet it touches.

When Venus conjuncts other planets, it adds grace and style and artistic abilities.

Mars revs up any planets it conjuncts, boosting vitality and the will to act.

When there are many planets in one sign, it is called stellium. Those traits should be sharpened, focused and dominant.