The tie rod connects your steering linkage to your vehicles wheels which allows the vehicle to be steered and for the wheels to move back and forth.
When the tie rod on the vehicle breaks then you lose control of that wheel and then your vehicle can go out of control which can cause you to roll your vehicle or cause you to go off the road and crash.
The crash could be fatal or severely injure yourself and others in the vehicle.
So having a tie rod break is a serious thing if you're going down the highway but if you're just driving down a town street going 5 or 10 mph then you won't usually wreck the vehicle but you'll have to have the vehicle towed.
A bad tie rod will show symptoms such as steering wheel shaking and excessive tire wear due to the vehicle being out of alignment.
When you replace the tie rods it's best to replace all tie rods at once because if one breaks then the others will likely break next.