What is a Registered Dietitian?

I feel as though I've been getting this question a lot lately, so I thought I'd answer it here. 

When I tell people I'm an RD, it's often followed by:
Oh, so can you make a meal plan for me? What's the best diet? What supplement/meal replacement company do you work for? Is dairy bad for me?

All these things have a role in what we do, but really we do SO much more!