Who was King Edward I and what did he do for England?
There were no less than seven English kings of that name. Which one do you mean? You can find them all in any encyclopedia under "Edward."
Eight. The last one abdicated.
The question asks "Who was King Edward I" - He was the son of King Henry III and famously fought Simon de Montford in the Battle of Evesham in 1265. He was more like Tony Soprano than the Monarchs we think of today and could not be trusted.
What did he do for England? He took most of its wealth and spent it advancing his realm; the Welsh Wars of the late 12th Century brought about many new Castles which still stand to this day. The film Braveheart highlights the endeavours of William Wallace who was opposing English governance of Scotland. It was Edward I who laid claim to Scotland and who eventually had Wallace executed.
Edward I died in 1307 in Carlisle whilst journeying on to yet another brawl with Scotland. His epitaph reads "The Hammer of the Scots" although it's moot whether he truly conquered Scotland as he did Wales.
King William I of England, at the time William II of Normandy claimed that King Edward the Confessor had appointed him as his successor as king of England. When King Edward was dying he proclaimed Harold Godwinson as king instead. William invaded England to claim the crown and defeated King Harold at the Battle of Hastings. He became king through right of conquest.