What Is Their Main Difference?
We use 'anything' to refer to an open, unlimited set of things that we do not mind what that thing is. It can be a thing either seen or unseen. We use 'anything' with a singular verb.
'Anything' is usually used in questions and negative sentences.
Can I do
You can do
We don't have
Remember that 'anything' referred to the presence of something (it does not matter what), it can be seen or unseen.
On the other hand, 'nothing' refers to the absence of something, it means there is not a thing. It can also be seen or unseen too.