The Prophecy of the Chosen One, also referred to as the Prophecy of the Son of the Suns, was a prophecy that spoke of the coming of a savior who would bring balance to the Force. The only known keepers of information regarding the prophecy was the Order of Dai Bendu and later the Je'daii and Jedi Orders. By the time of the Clone Wars, the Jedi Order believed that Anakin Skywalker was the one spoken of in the prophecy. Anakin Skywalker would later fulfill many of the written prophecies, thus proving he is the One of the Prophecy.
Written Prophecies with Anakin Skywalker's fulfillment's
1.
When the shadow of Bogan falls upon them, Ashla will not desert them because in the time of greatest despair there shall come a savior, and he shall be known as the Son of the Suns."
—Ancient Scripture
Bogan prepares for his rise to power by using the Sith to gain power for thousands of years, but Ashla sends the Chosen one (Anakin Skywalker) to defeat him once and for all in the end.
2.
In the time of greatest despair,
a child shall be born
who will destroy the Sith
—Ancient Scripture
Anakin Skywalker defeated Emperor Palpatine thus temporarily bringing balance to the Force, he would later return to the Galaxy to defeat the Dark Side once and for all.
3.
And the One shall march into the Temple with the Army of One Face.
—Ancient Scripture
Anakin Skywalker marched into the Jedi Temple in 19 BBY leading the 501st legion of the Clone Army.
4.
And the flames shall consume him, but he will be reborn.
—Ancient Scripture
Anakin Skywalker was severely burned on the volcanic world Mustafar, but later is encased in life support armor keeping him alive (not literally reborn).
5.
The Chosen One will be born beyond the Middle Rim.
—Ancient Scripture
Anakin Skywalker is born on Tatooine, which is in the Outer Rim, the Outer Rim is located outside the Mid Rim.