Is heat still being added to a liquid at the boiling point?

Yes. Heat is being added at the boiling point of a
liquid.

There is though, an important difference between
the effect of adding heat at a lower temperature and the effect of the addition of heat
at the boiling point.

This difference is that at a lower
temperature the addition of heat results in an increase in the temperature of the
liquid. This increase continues till the boiling point is
reached.

At the boiling point when heat is added, it does
not cause an increase in the temperature of the liquid. Instead, the heat is used by the
liquid to change state to gas. The heat required for a change in state from liquid to
gas is called the heat of vaporization of the relevant
substance.