If you have been doing infant stimulation activites with your baby since birth then by 6 months your infant has been listening to you identify lots of objects. "This is your blanket." "This is a spoon." "This is a ball" Eventually as you name objects your baby will be able to identify them too. No, he cannot talk yet, but do not be surprised if he reaches for an object you name if it is in his sight.
Also, even if baby is paying attention to a toy if you say "Daddy!", don't be surprised when he turns around to look for Dad. That is when you will see that your baby really has been listening to and learning what your are saying. He understands that words represent objects and names respresent people. So keep talking and identifying, and baby will keep listening and learning!