We try to keep things as simple as possible, but by necessity have developed a bit of lingo. Here are the definitions for some words that you will see in the manual.

An assignment of a single query sequence to a single location in the reference tree. (Contrast with pquery).
A “placed query” sequence, with uncertainty. In practice this means a collection of placements and their corresponding confidence values (e.g. likelihood weight ratio, etc).
A collection of pqueries. Short for a run of a placement program.
query sequence
The sequence getting placed into the reference tree. Typically a short read.
reference tree
The fixed tree on which placement occurs.