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hmmm.... cable shield is the braided wire which exists in shielded cables. This braided wire encloses the signal carrying wires, and protects them from external EM interference.
I'm sure your textbooks and Google will tell you the rest.
"Case" usually refers to the box or enclosure that the circuit is housed in. In most countries, this would be connected to the safety ground in the building's electric service. Often the case ground and the circuit ground are the same thing. But sometimes that case has a separate ground connection from the circuit for various reasons.