"OEM" or Original Equipment Manufacturer are products that the original manufacturer makes themselves or is made directly for that manufacturer.
"AMP" is an acronym that stands for After Market Product. These are products that are sourced out to third-party manufacturers which cuts out the original manufacturers hefty markup. AMP equipment works exactly the same as its OEM counterpart!
Here at Pond Supplies 4 Less we like to offer you the choice of the OEM and the AMP version of products whenever possible to save you money.