How does taxes work for investing in US Stocks?

I wanted to try investing in US stocks since fi had released their no platform fee offer. They also allow to invest even $1 in any stock. I have already added $40 to the wallet to invest in something like Nvidia. How would be taxes charged for me. What are the criteria in which a person would be needing to file return? Should we still file even if we invested a small amount? Help me here.