Purple vs Blue Items

Can someone explain to me the difference between and item that drops with Blue letters vs one that drops with Purple?

Thanks

Blue is a common unidentified..purple is slightly rare sometimes unidentified and yellow is rare(when its yellow the drop title includes the word rare) sometimes unidentified ...basically u have a better chance at getting something good like a major or superior rune with armor drops and rare weapon upgrades or rare weapons themselves such as Dragon swords