what is the trust store

i have a iphone 6 and its running on iOS 9.2.1. it has a 'trust store' on 2015090100, is this correct as ive read on the internet that the current trust store for ios 9 is 2015071300 and that the trust store 2015090100 is a 'pluggin'. any advise on this matter will be appreciated as ive visited an apple store and they were unable to confirm either way.