With most airlines, you can bring a small handbag/backpack into the passenger cabin.
However, some airlines only allow one item to be brought onto the plane, even if the booking includes a trolley for the passenger cabin. This means that in these cases, the airline permits you to bring a trolley into the passenger cabin but not an additional handbag/backpack.
In your confirmation email (or on the payment page if you haven't placed a booking yet), you will find information on whether two pieces of luggage can be taken on your flight.