Although Apple allows users to limit ad tracking within its new operating system, iOS 6 — here's an easy how-to — we still don't know a lot about what advertisers can see and do with the new Identifier for Advertisers (IFA or IDFA)

Here's a guide to everything that's currently known about IFA.

Bye Bye UDID

Prior to iOS 6, Apple products used Unique Device Identifiers (UDID) to allow advertisers to track users' habits and preferences. Basically, apps would sell UDIDs to advertisers.