The term heat defines a quantity of energy (this quantity of energy has a special property) transferred and the temperature is generally defined as the sensation of heat, however the definition of temperature based on sensation only is somewhat not a good approach.

You can see the direct relationship of the kinetic energy of an ideal gas and the temperature in the kinetic theory of an ideal gas.

The quantity of energy as heat has a special property which is it always flows from the hotter region of a body to colder region of the same body or another body in contact.

Therefore, the heat has the flowing property - we can not say that a particular quantity of heat is contained in a body but instead the heat is defined as the energy transferred from hotter body or region to colder body or region due to temperature difference. Thus, heat is the energy in transit.

You may think the temperature and heat are the same things in everyday language, but it's not true. Since heat is transferred from hotter region towards colder region, you can not say that a particular heat is contained in a body.

So consider a particular amount of heat is transferred to a body and all parts of the body reach thermal equilibrium. When you cut the body into halves, both halves will have the same temperature but not the the same amount of heat.

If two bodies have the same temperature, they are said to be in thermal equilibrium with each other. The Zeroth law of thermodynamics tells us that if body \(A\) is in thermal equilibrium with body \(B\) and body \(B\) is in thermal equilibrium with body \(C\), body \(A\) and body \(C\) will also be in thermal equilibrium.