Hephaestus is known as Zeus and Hera's son, although he was conceived without Zeus' help. He is also known as Vulcan, and the god of volcanoes, which makes sense since he was primarily worshipped in Athens and other volcano-ridden areas of Greece.
He is also the god who is given the credit for "helping" Zeus with his headache, taking a an axe to Zeus' head and splitting it open making the way for the birth of Athena.
He is the god of fire, especially blacksmith's fire, and is the patron god of craftsmen--especially those who work in metal crafts.
Hephaestus is known as the lame god, and his injury was received when one of his parents threw him down Mount Olympus--he fell for nine days and landed in the sea where he was rescued by Nymphs. The stories report different versions--one is that Hera was displeased with her son's appearance and so she threw him down the mountain; the other is that Zeus was angry with his son for siding with Hera in an argument against Zeus.
Hephaestus is the god of blacksmiths and fire. He is the god whose primary purpose is to create and forge out of fire and metals. Traditionally, he is asked by the Olympians to forge shields, swords, thrones, or any such item that can has to be created by extremely nuanced craftsmanship. He is responsible for the building of Olympian palaces as well as the most sacred of armor. His symbols are an anvil and forge, and due to a childhood accident, he has a lame foot. He is considered to be a God whose physical appearance is not considered beautiful or aesthetically pleasing. Yet, he is one who exacts a great deal of respect from the Gods. When Zeus needed to punish mankind for its role in tricking him, he commands Hephaestus to make Pandora, the first woman who unwittingly unleashes all that is painful on mankind.