Honoring one's parents refers mainly to our behavior toward our parents when they are old.
When a son/daughter is serving or assisting his parents he should do so with happiness and a positive body language. If a son or a daughter helps his parents making them feel that they are a burden, untold emotional pain is generated for the parents, especially when they depend exclusively on this son or daughter.
The Rabbis explained that we should talk to our parents softly, using nice words and with the respect one owes to a higher authority.
When the parents come to visit one's home, they should be welcomed with love, and honor and the son or daughter should be mindful to teach their children to honor and respect their grandparents.
Once I heard a beautiful explanation on the 5th of the 10 commandments: the Tora says: "Honor your parents lemaan yaarikhun yamekha", which is usually translated as: "Honor your parents so you will merit long days on earth..."
The alternative reading is: so will you merit when you've lived long days on earth". In other words: Honor your parents and you will merit to be honored when you grow old, because your children will honor you the way you have honored your parents.
In my experience as a rabbi I learned that this is a rule with almost no exceptions: when we grow old, we will be treated by our children they same way they SAW we treated and honored our own parents.
Rabbi Yosef Bitton. YMJC | 130 Steamboat Rd. | Great Neck | NY | 11024