Webflow has a strongly-typed approach to CMS content.
Numbers, Dates, Emails, Urls, Colors, are all “data types” that can be used as fields in the CMS. Each of these can be used in specific ways, and bound to specific attributes of specific elements.
Let suppose you have a collection list that is bound to a Collection named Recipes. In that collection list, you put a Link element on the canvas.
Different attributes of that Link element can be bound to different fields in your Recipes collection.
When you're in the designer, binding an attribute, Webflow will only show the field types it allows you to use from that specific Collection, and for that specific binding.
Text and Rich Text field types are different, and bind differently.
If you have a Rich Text element on in your design, it can only be bound to Rich Text fields in your collection.
Plain text elements, headings, link titles, and other text things can only be bound to plain Text fields in your collection.