I have a 2006 Ford Taurus and the heat went out, what would cause this..?

Sure, check coolant level first. But if that's ok, check under the dash and find the blend door actuator. It's a black plastic motor that opens and closes a blend door. They fail quite often and they're less than $40. Three screws and it pops off. If the motor opens and closes the blend door, your problem is elsewhere. But if you rotate the temp knob from cold to hot and the door doesn't budge, you've found the problem

The coolant level is low. Find out if there's leak.

The thermostat doesn't work and the temp gauge doesn't come up to normal either.

The heater core is clogged.

There could be a valve in your car that shuts off the water to the heater core.

Stay on top of this.

Never overheat it, just stop driving or a big expense can be caused.

Bruce is on the right track. There are myriad problems that could cause the heat to stop working. Start with the obvious and simplest ones first. When you get to a point where you run out of things you can do yourself, call a pro.

shortage of water.