When you turn on Automatically Share Recipe Details in MealPlan, here's what happens.
When you create a new recipe or edit your recipe details (such as the grocery list), that data will be sent to the MealSteps website. This site is run by the developers of MealPlan and is the recipe search engine used in MealPlan when you search for recipes online.
Why would you want to share your recipe details? Because once your recipe data is available on the site, the next time someone searches for a recipe like the one you've just created (using MealPlan's option to Find Recipes Online), they'll find your recipe. Your recipe's notes and grocery list will be added to their copy of MealPlan, saving them the time of building up the grocery list.
The more people participate, the more likely that you'll find a recipe that you like, with a grocery list all ready to go. This is a huge time saver.
Note that this involves granting us a license to use the data you've submitted. The data you submit is still yours - you retain rights to use it and you can use it as you see fit - but you grant Fall Day Software a license to use it as needed to run the site.