The blame has been pinned, squarely and often, on inadequate oversight of U.S. financial institutions, which created ever more complex and risky mortgage instruments, lured people to buy homes they could not afford, and brought the economy crashing to the ground.
Motion on the Earth does not take place in a vacuum. When one thing moves, it moves through or across another. When a wheel turns on an axle, the two surfaces rub against one another. This is called dry friction. Grease can be used to separate the solid metal parts, but this just reduces the problem to layers within the grease sliding past one another.
It's a measure of the forces that cause an object to rotate. Reaction torque is the force acting on the object that's not free to rotate. An example is a screwdriver applying torque to a rusted screw. With rotational torque, the object is free to rotate. Examples include industrial motor drives and gear reducers.