Answer:
When the worker is "alienated from his product" it simply means he loses every and any claim or right of ownership that he under normal circumstances would have over such a product.
This ususally happens because, in Capitalism, the capitalist or employer purchases the workers labour and it's results therefrom. What the capitalist owes to the worker is limited only to the financial rewards agreed upon. Financial rewards may be salary or wages.
All other proceeds arising out the relationship including the workers "product" belongs to the Capitalist.
Cheers!