What does the BinTableHDU store? I'm just getting started with very primitive analysis of FITS data, and I have a 'raw' FITS file which I don't know how to get different wavebands of data from (if this is even possible).

Filename: casa_raw.fits
No.    Name         Type      Cards   Dimensions   Format
0    PRIMARY     PrimaryHDU      33   ()
1    EVENTS      BinTableHDU    793   14621280R x 19C   [1D, 1I, 1I, 1J, 1I, 1I, 1I, 1I, 1E, 1E, 1E, 1E, 1J, 1J, 1E, 1J, 1I, 1I, 32X]
2    GTI         BinTableHDU     28   2R x 2C      [1D, 1D]

Could anyone explain what exactly this information conveys?
This shows that the file contains 3 Header-Data Units (HDUs; you can read more about this here). The headers contain meta-data. The primary HDU (0) has some 'cards' (basically keyword/value pairs most of the time, or comments) but no data. The next HDU (1, called 'EVENTS' in your file) is a binary table which contains 19 columns. Finally, the last HDU (2, also called GTI) contains another table with 2 columns. You can access the data in one of the columns of the EVENTS table using for example:

from astropy.io import fits
hdulist = fits.open('myfile.fits')
hdulist['EVENTS'].data['colname']


where colname is the name of one of the columns. You can find out the column names by looking at:

hdulist['EVENTS'].data.names