Hertz measures cycles per second - one Hertz is one cycle per second. Unlike gauss that is a measurement unit for the strenght of a specific thing (an electromagnetic field), hertz is a generic frequency measurement.
Prepend is a word that means to attach content as a prefix. It is often used in different kinds of programming and in automated processes. Some prepending is done manually as a user. For example, a prepend command could be used in a scripting language that a programmer would enter into a certain function or code module. It would add certain characters of text to the beginning of some variable or object.
An Append Query is an action query (SQL statement) that adds records to a table. An Append query is often referred to as an Insert Query because the SQL syntax uses the INSERT INTO command. Append Query Option when Designing Queries in MS Access 2013.