Thermal paste is a substance used to improve the heat transfer between a computer processor and its heat sink. It fills in microscopic gaps and imperfections on the surfaces, ensuring better contact and efficient heat dissipation. This helps prevent overheating and maintains optimal performance. Applying thermal paste is essential during the installation of a CPU or when replacing a heat sink. It usually comes in a tube or syringe and can be applied in small amounts. Proper application can significantly enhance the cooling efficiency of a system, prolonging the lifespan of the components involved.