Hi Kimberly,
RGB = red, green, blue - the standard for blending light such as from backlit screens and projected images.
CMYK = cyan, magenta, yellow, and blacK - the standard for blending inks, dyes, paints, and the like. This is the standard for offset printed materials, among others. Using CMYK colourspace, there are a host of colour 'systems' that have been devised for blending colours, each with their own pros and cons. Pantone, Focaltone, Trumatch are just a few but they are each well known and well used by specific segments of the 'printing' industry.
There is a lot of physics behind it, but perhaps the main point to consider is that what can be achieved with one standard will have its limitations in the other. Crossing over from one medium to another will render an approximation which in most instances will look very close to most peoples' eye. The tricky part comes when you try to push the limits of one medium or the other because what one does best the other cannot. You can stay within the limitations of RGB and CMYK-based media by playing it safe and only choosing colours capable of being rendered accurately in both. Being a media company however, you may wish to 'max out' the capabilities and presentation of your screen-based imagery/branding, especially since you work in high definition - put your best foot forward, as they say. I could go on (and on...) but I hope this helps as a starting point.
Cheers, Steve.