We have had several discussions about it... don't feel like you are alone in being a bit confused! The Yellow Card is for people in wheelchairs or ECVs who do not have a GAC that includes a FastPass access stamp. When they get to a FastPass Attraction, they have the option of getting a Yellow Card instead of a FastPass, which allows them to use the FastPass line at a time equivalent to the standby wait time. Read on, there are some very good explanations in other threads.
Thanks Teri for explaining. I was confused also. I don't need a GAC but I do use a wheelchair. If I understand this correctly, you get the yellow cards at each attaction that has Fast Pass. Is it also correct, that you would only get a Yellow Card if the Stand By wait is over 20 or 25 minutes? Is the purpose of the yellow to space out wheelchair and ECV users who need to use the special accessible ride cars?