A trophy is usually given as an award to recognise an achievement eg. winning an event or race. A trophy is usually made of wood, plastic and metal and themed relevant to what the award is for. A trophy can also have a plaque placed on it which can then be engraved with the details of what the award is for and also who the winner is.
A perpetual trophy is one which is given out each year with a little plaque to indicate the winner for each year. The trophy is then returned at the end of their winning year and it is given out again with the new winners plaque also attached. This way by looking at the trophy you can see the history and winners of the award over the previous years.