For your purposes, none of it matters. Essentially, your employer has negotiated a deal where for x% off, you are booked into a seat in C. Because the code can't be used anywhere outside of your employer's enrolled corporate TA's chosen interface, you are really seeing more information than you need to see.

You can use other search engines, including, .com, for the purpose of researching routing, but you will always have to return to GetThere to determine whether what you want can be done under the rules your employer has set and for the price point you (or your employer) is willing to pay.