Paul is telling Titus that the different kinds of people in the church have different rolls to fill. The older should teach the younger, while slaves are to do their work well and honestly.
We have responsibilities in the church as well. To some, we are the older ones and to others, we are younger. We are to be faithful to God in all we do and look for ways to help those who are less experienced in their faith. We all live under the authority of others and should do that in ways which make Jesus look good.