Nicolas,
Layer Leadin Settings - shown on page 23 of the manual, also see Tutorial #7 as gives examples.
A lead is a series of tool / axis axis movements before actualy machining a contour or a pocket. So on approach to the contour it is a leadin and leaving the contour it is a lead out. The leads have to do with programing methods of moving the tool. Both provide for where a cutter offsetting wil be applied or canceled. So there are some rules which apply to the programing. In LC a pocket or contour is usualy on a layer and additionaly you can set LC on import to automaticaly add them.
Spindle speed in LC will always refer to how fast the spindle is rotating the tool. In that way it is very specific as whatever the spindle is ie; chuck, mill head, router, holder, is the source of rotation and can't be confused.
In the case of having a way of controling the speed via Mach, the proper speed is specified and the associated coding is provided in the Gcode.
In the Tool Dialogue you specifiy the feedrate and plunge speed. I don't give any specifics or recomendations.
Like ostie said, you need to experimentor find a reliable source for information. For metal cutting these can be calculated, charts used based on experimentation and experience. It can be quite involved.
For wood you want to remove / cut chips and not chunks, not burn the tool or the wood. It also is related to the feedrate ( how fast the cutter is moving into the work ). Even for wood/mdf/partical board it can realy vary depending on the density, grain, etc of the wood. Partical board has some nasty stuff in it and some of the adhesives and stone will do a number on a router bit. Heck, sometimes the is granite / stone in ebony, or some of the exotic woods can actualy be machined. When you manualy use a router you constantly vary the feed based on what you see, so experiment to see what words on your material.
There is a difference between plunging into a material with the face / bottom of the cutter as compared to
using the side of the cutter when feeding.
You should be able to find some generic guidelines for machining wood on the various web sites that sell machines.
As far as the manual goes and definition of terms.........I was asked to define all the terms but did not. The manual was meant to show the user how to use the software....i did try to add some machining experience or practical application in it.....but, to define "all "the words.......maybe someday.
But for now, i am done and need a break from it.

RICH