Beginner: AXIS and basic homing

As a newbie, I understand the concepts of machine home and work origins (at least I think I do). I just have trouble with the practical implementation within AXIS. I don't think this is a problem with AXIS - its just my lack of understanding and AXIS is the default GUI that I use.

My questions are:
1) when the machine is just switched on - does the machine know in absolute terms in the XYZ 3D-space where the Control point is - or is the "turn-on" position of the control point set as X,Y,Z = 0,0,0.

My particular problem is:
I 've created a 2D image in Inkscape and used Inkscape Gcodetools to create the G-code for the machine. This image is for engraving onto 30mm diameter keyring disks. The image is positioned relative to the XY (0,0) origin in Inkscape so that I could use the 0,0 position as the engraving starting position over the keyring link hole at the edge of the blank disc. The G-code conversion and GUI image are loaded without problem into AXIS with the control point cone positioned initially over the 0,0 image position.
2) So how do I now set up the control point to sit over this image 0,0 point (i.e. the hole in the blank disc) and commence to engrave successfully? If I move the X,Y,Z stepper motors to place the Control point over the hole and home the axes, the "cone" in the AXIS image window now is somewhere else away from the original X,Y = 0,0 of the Inkscape image and commencing a test engraving run puts the tool in completely the wrong place.

I guess I'm asking how the "Home axes" and "touch-off" interact and what is the sequence I need to follow to a) let the machine know where the "Control Point" is and then b) to move the "Control Point" over my image starting position (X,Y = 0,0 - which I presume is somehow known to the G-code instructions) for successful engraving at the right place.

The first thing you have to do is Home the machine so that it knows where the tool is located within the work space.

Next you set your work offsets so that your 0,0,0 point is located where it should be based on your setup in the G-Code. So in this case you want to move the tool so that it located over the center of the hole in your disk and "Touch Off" the x and y axis so that it sets the G54 offset or what ever offset coordinate system you are using to 0,0. You will also have to "Touch Off" the z height so that your tool is at the appropriate depth when you are engraving. Tool length offsets will also come into play if you have them set.

See the following.

www.linuxcnc.org/docs/html/gcode/coordinates.html

Be sure to do a trial run (cut air) first to prove that you are doing the steps correctly.

note:

touch off on Z is usually done on the top surface of the work , so all cutting depths are negative values .

Thanks to Nitromethane and cncbasher - it's so much less opaque now - and thanks for the link. I have a copy of the pdf LINUXCNC V2.7 Manual on my PC and I thought this would be the best source of information - but the description of "Homing" at 1.3.3 on page 21 was very brief (4 sentences) and didn't really help me. The html site is much better and I will endeavour to go to this site in future for my information and stop pestering people with these basic questions - you would have been within your rights to have just posted RTFM.

you'll find people here are helpful , rather than throw a load of paper to read .. , and in anycase you can have it in pdf or whatever , but if your a new person to the subject
you would still be lost in the soup ! , dont worry everyone was a newbie at some stage , you may feel it's a silly question , but your probably not the only one looking for that snip of information
that switches the light on .

Enjoy Linuxcnc .