When we run our dishwasher/washer, our toilet begins to "bubble". What does this mean, and what do I need to do?

"When we run our dishwasher/washer, our toilet begins to "bubble"."

You have a partial clog downstream from the bathroom.
What's happening is that the washer/dishwasher hits the clog and bounces back sending a bubble of air ahead of it. That's what you see in your toilet. After the discharge hits the clog it then drain s away. The clog can only get worse. They don't heal themselves.
The drain line will have to be snaked out from the lavatory roof vent. Put out enough cable to get to the base and 20 feet more. Test and flush the line by cycling the washer. Good luck, Tom