How about this?
http://pcbheaven.com/wikipages/How_Key_Matrices_Works/
First google result 
Thanks and I understand, a bit. I find it really difficult to understand how it works. I really need some real life pictures.
Think of the wiring like a spreadsheet or a table.
You have rows and columns. If you look in the "A matrix in real life" on that page it shows a little drawing with the controller and some switches, while it's not real life pictures, it is an accurate representation of how it's wired. Each yellow dot is a switch. Each switch has a corresponding row and column. You can see all of row 1 is on pin 1 but the columns are on A B C D. When you press the top left button it completes a circuit from pin A to pin 1. The firmware sees a signal from A-1 and it will send the appropriate keycode based on your layout.
When you configure the keyboard firmware you have to tell it how your individual matrix is wired. The pins you pick on the teensy don't matter, just pick pins and take notes. Once it's all wired up you have to edit the firmware code to tell it what pins you picked for your matrix.
just be sure all of your diodes are facing in the same direction. I don't even think the direction matters as long as they are all the same. I say this because it can be reversed in the firmware. If you pick a direction that's different from what you load on the teensy, it's as easy as flipping it in the firmware assuming you put them all in the same direction.
Give that article a thorough read and let me know if you have any questions.
