A Capture One Process Recipe is a collection of settings that defines the outcome of processing. Parameters that are stored in a recipe include file format, quality settings or bit depth, ICC profile, size, file location, naming, and more. They provide an easy way to export photos from within the standard editing workflow.
By collecting parameters in a set, and the ability to create multiple sets or recipes, you can easily switch between recipes. You can even combine them to create multiple output files simultaneously, with optionally different naming and in different locations.
To summarize, recipes are extremely powerful but due to their history and evolving nature, possibly complex at first sight!