Pre oilers

[vettestr]

Malcolm,
Welcome to the club and your 1st post. There are slight differences and different manufacturers so here is a global answer. The idea of this is to store pressurized oil in a remote container of 1 to 3 qts. The manual or electric valve seals the oil from the engine until you want it.
If you open the valve after you start the engine the oil pump generates a pressure equal to or higher than what is in the tank so there is no flow unless a problem of some type happens. If it does have an issue then the oil dumps in engine to keep it from starving for oil until you can shut it down. You must close valve before shutting down engine for next cycle.
If you use it as a pre oiler then you open valve to get pressure after it was sitting and then start engine up. The use of electric valves and pressure sensors or lights allow you to use this in many different ways or allow it to function when predetermined set points are met. I also think it has just as much of a benefit to your street car or stock grocery getter.
Hope that fills in most of the blanks for ya.