Two bodies are in thermal equilibrium with each other if there is no thermal energy (heat) transfer between them. This happens when the two bodies are at the same temperature.
If the two bodies are not at thermal equilibrium, they will exchange thermal energy until thermal equilibrium is established.
Thermal energy that is transferred from one body to another is called heat. Heat always flows from a hotter body to a colder one.
Placing a cold spoon in a hot cup of coffee causes the spoon to warm up until it reaches the same temperature as the coffee.