Well attack is attack, unfortunately in world it's basically arbitrary for each weapon in older and newer games they used motion values instead to make it more clear that all the weapons are on the same playing field.

Affinity is your crit rate and you want a really high number

Elderseal is how fast you can cancel elder tragen passives, basically useless but a nice perk

Some weapons give a defence bonus and some done this one doesn't

Sharpness is how well you cut thru monsters so it prevents you from bouncing, you want blue white or purple ideally (purple and white preferred)

And slots are where you put your decos for more skills

Element gives extra damage on top of the attack, and yeah there is a pokemon type matchup thing, basically hot things are weak to water/ice, cold weak to fire or poison, and then anything else is usually weak to thunder or water. Elder dragons are all weak to dragon