Is there any documentation available which explains what capabilities each permission actually grants? I ask because some permissions have rather vague names.

Example 1:
I have discovered by trial-and-error that the permission "Design web site" is required for a user to have access to the template fieldset in the Properties > Template tab of a document.

But I don't precisely what _other_ capabilities are granted by checking

Example 2:
What do Create, Delete, Modify and Read mean, in the Modules > Administration matrix?
What does this allow someone to create?