For every field you create, we create a "Snippet" liquid template. If you need some code to get your theme customization started, or just need the namespace for a particular field, there are two ways to get it.
Assuming you're looking for information about a field attached to a product, go to Products -> Install -> Manual Install -> Advanced.
Within the app, we provide a theme snippet editor for each field. Within the editor, we also provide this information. Click on +Configure Fields > Edit