Charcoal/grit for atiel?

I recently got a pet bird, a atiel. She's about 6 months old now. My parents had a atiel for over 20 years. They gave me a list of things to get my bird, and on it was oyster shell grit and charcoal. Now, their bird lived for a long time and was given charcoal daily (not sure about the grit). But I read online that grit is only for wild birds that swallow seeds whole, not pet birds that break into seeds. It seemed to suggest it would do more bad than good, too. Is charcoal considered grit and are they both unnecessary? Or should I have at least one for my bird and if so, which is better? I'm confused. Can anyone explain this for me please?