[Advaita-l] What is consciousness or chaitanya?

[The Crimson Universe]

Namaste, Greg here.
Advaita says, you are the consciousness. You are chaitanya.

My question is -
 What is the definition of consciousness or chaitanya in Advaita?

Modern Science and even Buddhism, equates consciousness with the human
mind, since according to them, its the mind that always remain conscious or
aware of everything around it.

But Advaita says, consciousness or chaitanya is different from the mind.
Please explain to me, how is it so?

Thank you.