Heat

Heat is the flow of thermal energy and it flows from a high temperature to a low temperature.

If two objects are at the same temperature we say that they are in thermal equilibrium and no heat flows.

If object A is in thermal equilibrium with object B and object B is in thermal equilibrium with object C then A and C must be in thermal equilibrium with each other.

Get into a hot or cold bath and energy is transferred:

In a cold bath thermal energy is transferred from your body to the water.

In a hot bath thermal energy is transferred from the water to your body.

As the energy is transferred you and the water become the same temperature. When this happens there is no longer a flow of energy so no more heat. You both still have a temperature due to the vibrations of your particles but there is no longer a temperature difference so there is no longer a flow of energy.