What are heating mats or germination mats? Must I use one to get seeds to grow?

Many, or perhaps most, seeds like heat to germinate best. Special waterproof electric heat mats are available at most major catalogs that sell seeds (like Johnny’s, for instance, and are placed under the seedling trays after seed is sown during germination. The mats raise the temperature in the area inside the flat about 20 degrees above the room, or ambient, temperature. This is certainly more fuel-efficient than heating up a whole room hot enough to warm the tiny cells of soil to the desired degree, so mats are a great tool. Not essential, but helpful and efficient for germination.