Shims are very useful for people who often change CPU, heatsink and/or cooling solutions, or use a heatsink that is heavier than the CPU manufacturer's recommended weight.
Silicone oil-based thermal grease can be removed from a component or heatsink with an alcohol (such as rubbing alcohol) or acetone.
In computing and electronics, thermal pads (also called thermally conductive pad or thermal interface pad) are a pre-formed square or rectangle of solid material (often paraffin wax or silicone based) commonly found on the underside of heatsinks to aid the conduction of heat away from the component being cooled (such as a CPU or another chip) and into the heatsink (usually made from aluminium or copper).