"Inner Spring" is a more general term. It refers to any support system inside a sofa cushion or mattress that uses metal coils or springs.

Pocket Spring is a type of Inner Spring system.

Think of it like this:

• Inner Spring is the category (e.g., "Vehicle")
• Pocket Spring is a specific, advanced type within that category (e.g., "Electric Car")

Other types of inner spring systems include:

• Bonnell Coils: The oldest type, hourglass-shaped springs connected with helical wires. Common in entry-level furniture and mattresses. They can be noisy and transfer motion easily.
• Offset Coils: An evolution of Bonnell coils, with a squared-off top and bottom designed to hinge with the movement of the body. Better than Bonnell but not as isolated as pocket springs.