The NYT's blog `The Learning Network' is looking at words that are both noun and verb.
Overview | In this lesson, students play with words that can function either as nouns or verbs, depending on context.The idea here is good, but the wording is unfortunate. Words don't `function as' nouns or verbs; that would be like saying I function as a male or a particular animal functions as a dog. Rather, the words are both nouns and verbs. You could also say they belong to both categories.
When we start to talk about function, now we're into the territory of subjects, objects, modifiers, complements, etc. If you want to dig deeper, have a look at these tree diagrams with a complete list of categories and a complete list of functions.