Short answers, pulled from the story.
The original name of Excalibur in the earliest Welsh tales was Caledfwlch, a compound of words meaning hard and cleft. Geoffrey of Monmouth first Latinised the name as Caliburnus in his 1130s Latin chronicle Historia Regum Britanniae. This transformation eventually evolved into the familiar Excalibur through centuries of French and English retellings.
The first known tale to feature Excalibur embedded in a stone appeared in Robert de Boron's French poem Merlin around the year 1200. In this account, the sword was pulled from an anvil sitting atop a stone that appeared in a churchyard on Christmas Eve. This motif was later adopted by British author T. H. White in his 1938 novel The Sword in the Stone.
In the Post-Vulgate Cycle variants, the sword from the lake was hurled into the pool at Camlann or Salisbury Plain by Griflet. In the English Arthurian tradition, the motif of throwing the sword into the lake became attached to Bedivere or Yvain in the chronicle Scalacronica instead of Griflet. A woman's hand emerged from the lake to catch Excalibur before Morgan appeared in a boat to take Arthur to Avalon.
The scabbard of Excalibur had powers that prevented any wounds received while wearing it from bleeding at all. Merlin chided Arthur for preferring Excalibur over its scabbard because the latter was the greater treasure. The scabbard was stolen by Morgan le Fay and thrown into a deep lake, which left Arthur vulnerable to the fatal wound that ended his life.
Excalibur's blade shone so bright that it gave light like thirty torches when Arthur first drew it in combat. This luminous quality was recorded in Malory's Winchester Manuscript and served as a magical property that gave Arthur a decisive advantage in battle. The sword was said to have been forged in Avalon by the Lady of the Lake.
A sword identified as Excalibur or Caliburn was discovered during the exhumation of Arthur's purported grave at Glastonbury Abbey in 1191. On the 6th of March 1191, after the Treaty of Messina, either this or another claimed Excalibur was given as a gift of goodwill by Richard I of England to Tancred, King of Sicily. This event was one of a series of symbolic Arthurian acts by the Anglo-Norman monarchs.