Short answers, pulled from the story.
The Argonauts were a band of heroes who sailed with Jason to Colchis to retrieve the Golden Fleece, in the years before the Trojan War, around 1300 BC. Their name derives from their ship, the Argo, which was built by a craftsman named Argus. The crew included figures such as Heracles, Orpheus, Castor and Pollux, Peleus, and roughly fifty heroes in total according to various ancient sources.
King Pelias of Iolcus, who had usurped the throne from Jason's father Aeson, sent Jason on the quest as a trap designed to kill him. An oracle had warned Pelias that a descendant of Aeolus would take revenge on him, and the one-sandaled Jason fulfilled a separate prophecy he had received. Pelias swore before Zeus to surrender the throne upon Jason's return, expecting the quest to be fatal.
Medea, the daughter of the Colchian king Aeëtes, gave Jason a protective drug to anoint his body, shield, and spear so that neither fire nor iron could harm him for one day. She also told him to throw stones into the midst of the earthborn soldiers that would rise from the dragon's teeth, causing them to fight one another. On the night of their escape, Medea drugged the dragon guarding the fleece, took the fleece herself, and led Jason to the Argo.
The Symplegades, also called the Clashing Rocks, were massive rocky cliffs that crashed together by the force of the winds, closing the sea passage between them. The seer Phineus advised the Argonauts to release a dove first; if it passed through safely, they should row hard and follow. The dove lost only the tip of its tail, and the Argonauts rowed through in the interval, with Hera's help, losing only the tip of the ship's ornamented stern. After that passage, the rocks stood permanently still.
Talos was a bronze giant who guarded the island of Crete by running around it three times every day and pelting approaching ships with stones. He had a single vein from his neck to his ankles, sealed at the end with a bronze nail. Medea defeated him either by maddening him with drugs or by drawing out the nail so his ichor drained away; a separate account credits the archer Poeas with shooting him through the ankle.
The Argonauts completed the entire voyage in four months. They departed from Iolcus, sailed to Colchis by way of Lemnos and multiple ports of call, and returned between Euboea and Locris to arrive back at Iolcus.