TPR silicone is less than 100% silicone (sometimes as low as 10%). It's slightly porous and can't withstand the temperatures that pure silicone can, but it's less expensive and can be used to make toys that have a silicone-like feel. It can't be boiled or put into a dishwasher.
Pure silicone is 100% silicone through and through. It's more durable and can withstand over 600 degrees, is completely nonporous (so bacteria won't be able to hide anywhere on it), and with minimal care will last a lifetime. It's more expensive, but you can boil it (three minutes will do), bleach it (10% bleach solution), or put it in a dishwasher (top rack, no detergent) to completely sterilize it. Though with vibrators, you shouldn't use the dishwasher or boiling method to clean it, or the heat will most likely ruin the motor.