What did the space probe Giotto do?

Giotto was the first solar system exploration mission carried out by the European Space Agency. 

In 1986, the Giotto space probe was one of five probes sent to study Halley's comet. It flew through the cloud of dust and gas around the comet at 42 miles per second (68 kilometres per second), passing within 310 miles (500 km) of its icy core.