Edward II was the son of Edward I and his first wife, Eleanor of Castile. He was the first Englishman to hold the title of Prince of Wales. He became heir to the throne on the death of his elder bother Alfonso, and was equipped with the training to succeed his father, but he rapidly gained a reputation for frivolity and extravagance, as well as improper closeness with a Gascon knight, Piers Gaveston.
Edward I eventually exiled Gaveston, but his son brought him back when he succeeded to the throne, in 1307. He also abandoned his father's intention of a campaign against the Scots (then fighting a swelling campaign to re-establish their independance under Robert the Bruce).
As a king, Edward II lacked any obvious drive or ambition, which made him a poor comparison to his energetic (if authoritarian) father. He married Isabella of France, daughter of Philip IV, and with her had two sons and two daughters (one of whom, Joanna, became wife to David II of Scotland).
His relationship with Gaveston was resented by the English baronage (who were looking to flex their muscles after Edward I's firm hand on them). They wanted Gaveston exiled again, and in 1312 Edward's cousin, Thomas, Earl of Lancaster killed Gaveston in battle. Unfortunately the barons then sought to dominate the King, who found a new favourite in the Earl of Winchester, Hugh le Despenser.
Edward was indiscreet in favouring Despenser, and the barons had him exiled. Edward had him recalled and for a time obtained the popular support by working to rein in the baronage. But the Despensers (father and son) overdid their drive for power (including having Lancaster executed), and in doing so offended Queen Isabella. At the same time Edward was losing popular favour because of the rise in powers of the Scots, and his unwillingness to go to war with his northern neighbour.
In 1325 Isabella went to France with her son Edward to do homage for Aquitaine. That done, she declined to return until Edward dispensed with the Despensers. She grew close to one of the barons whom Edward and the Despensers had exiled, Roger Mortimer, and in 1326 she landed with him in Essex, and declared she sought revenge for the death of Lancaster. Edward's supporters deserted him and he fled to Glamorgan. Isabella saw to the execution of both Despensers and then the capture of her husband.
Parliament was summoned in 1327 to depose Edward II and make his son Edward III in his place. Edward himself was then compelled to renounce his kingly office, but this proved not to be enough for the queen, and in 1327 he was declared to have died. Rumour said he had been murdered by a a red-hot iron being introduced into his fundament. Modern rumour has had him instead whisked away to Ireland and Italy (via Corfe Castle) where he is supposed to have died naturally at a later date. One theory (contained in Alison Weir's biography of Queen Isabella ) even has him secretly meeting his son, Edward III, and reconciling with him before his death.
Edward was also unpopular with his baronage throughout his life for his liking for, and participatio in, rural pursuits such as hedging, thatching and the like. It was possibly this tendency which led to the attempt, by John of Powderham to usurp the throne.
NOTE: Mortimer survived for only a short period after Edward III's coming of age, and Isabella had to suffer a period of disfavour before being allowed, in 1330, to retire from public life.