mnbp gave you the info you need.

Basically, TSA PreCheck is a government program which allows you expedited security screening - keep laptop and toiletries in bag, keep shoes and light jackets on, walk-through metal detector instead of whole body imaging/scanner. This requires a background check and is available through TSA directly or is granted through other trusted traveler programs (e.g., Global Entry, Nexus, etc.). There is also a fee for the applications.

UA Premier Access (or really any airline status benefits) provides you with a dedicated security queue which may be shorter than the "regular" line, but it still requires you to go through the "standard" security screening - remove laptop/toiletries, take of shoes/jackets, whole body imaging. It also offers other benefits (boarding, baggage, mileage earning, etc.) not related to security screening. This is achieved through flying (usually), credit cards, status challenges, etc.