No problem, Brad:
Simply put, a Layered Process Audit is a check of a workstation (or similar) in a manufacturing process (assembly, welding, etc) by various 'layers' of management from line supervision to the top manager of the facility, to watch the operator 'doing' the process. These are done at a frequency which ranges from per shift (supervisor) to weekly/monthly. A simple audit checklist ensures the same topics are covered each time
plus any actionable items found, which are, in effect, escalated to top management each time they do an LPA.
An error proofing audit is a type of LPA but done by specific individuals (process technicians etc.) Typically it consists of running a known reject part down the process to 'trigger' any error proofing systems such as position detectors, vision systems, etc. Other systems rely on proximity detectors which can be 'fooled' and tested to see if the line still functions and will 'accept' defective parts.
The underlying reason for these 'audits' is to re-inforce operators 'following work instructions'............because some people think that's why we get poor product quality!
There are other threads here about LPA's (I don't know how to link them

)