I have one trine, eight sextiles, eleven squares, four conjunctions (which are all of close orb!) and no oppositions. I have a bowl chart, that's why.
Conjunctions are considered the strongest aspect, blending in the qualities of two planets (or more) in which they work beneficially (most of the time, unless it includes a malefic planet like Saturn or Pluto) for each other. Trines show the mutual or comfortable way of relating an inner need shown by one planet to the other. Sextiles are like trines, only that they are considered weaker than trines although indicates talent, natural ones.
Conjunctions, trines, and sextiles are considered harmonious aspects, with square and opposition being harsh aspects, meaning those which which most probably bring friction, distress, bad way of harnessing energy of certain planet functions, contradictory - generally negative stuff. The difference between the two harsh aspects are that squares cause abrupt flow of energy which doesn't flow steadily as that of trines (for an example) but suggest a high level of enthusiasm to go out and fix it, that's the pro of it. Oppositions on the other hand suggest a need for others to intervene in this aspect in order to make the best out of it, hence it relates a lot to relationships.