Run-off and Boil
After the mash stand, the sugars are extracted from the mash by spraying hot liquor over the mash. The liquor filters through the mash bed taking the sugar with it to form a liquid called sweet wort (wort is pronounced to rhyme with 'work').
The sweet wort is run into the Copper,  which is the vessel shown here. In the Copper, the sweet wort is boiled (for an hour) and hops are added - some at the beginning of the boil to produce bitterness and some at the end to produce hop aroma.