Tier

Tier - Abbreviated and combined with a number, expresses the general power level of an item.

T1: everyone can craft it, might need a profession

T2: can be crafted, needs Blueprint

T3: cannot be crafted, you can find T3 with stats

T4: cannot be crafted, even better than T3, you usually don't find T4 with stats

Examples:
Any Level 1 Character can craft a double-barreled Shotgun which is considered to be T1
Get first level of Small Guns profession and craft Combat Shotguns, which are also T1
But get Small Guns 2 and the right blueprint to craft the H&K CAWS which is T2
The Pancor Jackhammer is even better, and cannot be crafted, so it's considered T3
A crafted Minigun is considered to be T2 even with stats
Meanwhile, the Avenger Minigun is T3
The Vindicator Minigun is even better than the Avenger, so it is T4