How does the US government define work?

Question

I'm told that foreigners holding certain visas are not permited to work.

but what do they exactly mean by work? what if you establish a website that generate income but it does not necessarily have a formal business stuff?

Answer 1

Work is the performance of something that derives payment of wages.

Answer 2

Ditto.... A "Not Valid For Employment" means you cannot perform labor in exchange for money. Look up United States Code for a more detailed explaination.