How do resistances work?Follow

I just added +3 all resistances to my cloak. How does that help. Most of the enchantments in WOW seem to have better conditions in which they work. Is it better to have +3 resistance or additional armor (+50 armor). Does it matter if you are PvP or PvE? Thanks

resistances lower the amount of damage done to you if it is a certain type. lets say that something hits you with a fire spell, and you dont have any fire resistance. that spell would do less damage to you if you had fire resistance, depending on how much fire resistance is needed.