Difference between Track Matte and Image Matte?
 

These two effects seem to be the same, can someone explain the difference between the two? Is an image matte a type of track matte?

Bit of an update: When I make a greyscale shape in Photoshop and save it as a JPG and use it as an image matte, things work fine when it's set to "use alpha channel"

But when I use a track matte and use the same image, I have to slect "use luminance" for it to have any effect as "use alpha" doesn't do anything unless I make the shape in the title maker. I've also saved the file as a TIFF which I believe saves alpha channels...I've even made a photoshop file where I have a white background and I delete what I dont want (so the checkered pattern comes through, the alpha channel) but even that makes no difference...
I realize that it works if I set it to "use luminance" and if it aint broke, don't fix it...But what am I doing wrong?

I've just been using those features so maybe I can offer some help.

The difference between Track Matte and Image Matte is that Track Matte can use moving footage and Image Matte can only use still images. Yep, Track Matte can also use still images so I'm not sure what the need for Image Matte is.

When you make a Photoshop file and delete the image (so a checkerboard shows) that's transparency not Alpha Channel. To make a true Alpha Channel you have to select the channels tab and click on the Add Channels icon and then draw your Alpha Channel in black and white. (Or shades of gray.)

You also need to save your matte in a format that supports Alpha Channels (Photoshop, TGA, or TIFF) JPEG doesn't carry Alpha Channels.

Ahhh, Thanks a lot Eric!

And the difference between Colour and Chroma Key (*duck*)

The Premiere help file mentions that one of them only affects the alpha channel while the one doesn't, does this mean that the one with the keyed alpha channel can be used as a matte while the one with the keyed colour not affecting the alpha channel doesn't need to be used as a matte?

I haven't played with those features... you're on your own, sorry!