Grace you are just going to love eating on the
Disney Dining Plan on your upcoming Walt Disney World vacation this March.
In answer to your question, to dine
a la carte means you are free to choose individual dishes as you wish from the restaurant menu.
However to dine
fixed prix you are limited to dishes only featured within this already
fixed price menu.
You are always at liberty to make selections from the
entire restaurant menu whether it's included in your level of Disney Dining Plan or not.
Remember if you are at all unsure as to what's included, or if you will be charged extra for any items then I recommend asking the assistance of your knowledgable server who will only be too happy to help!
Have a great Disney day!
~ Jane