A drain tile system is a collection of pipes installed around your foundation. The pipes are perforated to allow water to drain into them. The pipes them run the water into an interior sump pit or onto the ground away from the house. Homes without a drain tile system or with a clogged drain tile system can find their crawl spaces and basements flooded.
Check your sump pit, if your home has one. Homes with sump pits are usually on level ground, preventing the builder from building a sloping drain tile system that moves water away from the home. Sump pits are usually in the basement. Check if the pit is full of water that isn't being pumped out quickly enough by your sump pump. Check the pit after a day of heavy rains, when clogs in the drain tile will be most evident.
Walk your basement, feeling the walls for any excess moisture. Move anything that is leaning up against the basement walls so you can check for leaking cracks. Water coming through cracks in the foundation is a sign that your drain tile system is plugged and isn't moving water away from the foundation into the sump pit or ground outside.
Find your drain tile system outlet, if your home doesn't have a sump pit. A drain tile system that doesn't empty into a sump pit usually juts out of the ground and lets gravity pull water out of the piping. Wait for a day of heavy rain, then check the pipe terminus. If water isn't flowing out, there's a clog. Wait for the rain to stop then look up the pipe with a flashlight to see if you can identify any clogs from dirt collecting in the mouth of the pipe.