A logging truck is a really big truck that is used to transport logs from a forest to a sawmill. The truck has a big open trailer on the back where the logs sit. The logs are tied down to the trailer to keep them from falling off. The truck driver sits in a cab at the front of the truck and drives it down the road. But because the logs are heavy and the truck is so big, it's important for the driver to be really careful when driving.
Logging trucks are important because they help move the logs from the forest to the sawmill where they can be turned into things people need, like furniture or paper. Without logging trucks, it would be really hard to move all those big heavy logs around.