It is a very old system:-
the X Window System used X BitMap (XBM), a plain text binary image format, for storing cursor and icon bitmaps used in the X GUI. The XBM format was replaced by XPM for X11 in 1989.
There are two ways of drawing things onto a matrix:-
1) By a program algorithm. That is setting each LED from some code. The code generates a sequences of addresses and sets the LEDs at these addresses.
2) By a pre programmed array. This is a block of memory that has had the zeros and ones already set by some other program and you just transfer this memory into the memory being used to refresh the matrix. In this case it is normal to have some other program, perhaps with a graphical interface that will generate these blocks of memory. The X BitMap is / was an attempt to standardize this process to allow exchange of data and thus patterns, in that case for icons and cursor shapes.
I try to learn and allready know how do display texts or circles or rectangles but just because i copy and pasted it. I dont really know what the code behind all that means.
The trick is to take what you copied and paste and try and make it do something different. Look at the code, try and read it line by line and try and make it do something slightly different. Only be experimenting with it yourself are you going to learn how to program.