In addition to providing the extra ball, extra "free ball time" is normally provided in a range of x seconds.
This "free ball time" as long as it remains lit, balls will continue to be directed onto the playfield, equivalent to a "novice" mode.
This is operator adjustable.
The settings are usually provided in the code as set under buy-in in pricing section of B/W games.
Number of buy-ins is also provided as an option, and the limit is provided in the code usually 1-9 (or zero).
All these functions are under the recommendation of not only the designer and programmer, but based on gameplay testing during sample periods prior to production to maximize earnings.

You can research this yourself using the operation manuals and operator handbooks on your own games.

There are also sometimes specific game features enabled, but this is completely title dependent.
You have to be extremely direct, as there are too many games to list, and different manufacturers handled this function uniquely.

Sometimes players are treated to extra sounds, screens on the DMD or both.
Other times additional play functions.
Other times, special scoring.

For example, in STTNG allows an immediate selection of an additional game mode prior to launching the ball.
This is a common functionality of most B/W games to allow players to see additional parts of the game, continue a mode, or reach a wizard mode.

Program and game designers do not post often on this forum for various reasons.

Don't forget to enjoy "Midnight Madness" on your JM.