Videl is the pure human wife of Son Gohan, and, more importantly, the spawn of Hercule Satan's mighty seed. She meets Gohan during the Great Saiyaman Saga, and is the first person to figure out the identity of the Ginyu ripoff. From that point on, she is a major supporting character and a source of motivation for Gohan.
According to that one idiot, Gohan, Videl has achieved the impossible feat of attaining more strength than her father. While this is clearly not true, it should be noted that Videl is much stronger than most humans, and able to channel her ki after training a short while with Gohan. She is able to fire weak ki blasts and fly, something that her father has opted not to do in the interest of making his fights more fair to his opponents.
Videl's name is an anagram of Devil, in line with her father, Mr. Satan's name.
As a side note, she was fairly cute before she decided to butcher her god-tier pigtails in a horrible attempt to get at Gohan's hybrid monkey penis.
Videl eventually became the great saiyawoman, assisting Gohan in his superhero shenanigans. Her job was mostly to stand around hoping not to get shot while Gohan took out all of the criminals. She got a punch or two in, occasionally, and had a much better costume.
Videl is the first known mother of a saiyan hybrid with less than half saiyan blood. Pan is born six years after Majin Buu's death, and is one of the main factors that allowed Goku to become a Super Saiyan God. Despite what GT may have depicted, she is not canonically a bland cardboard cutout who serves only to bitch at Goku and Trunks.
Videl shares several similarities with Chi Chi. Both are great human fighters who still fall flat compared to all of the Z-Fighters, both marry aliens and have powerful hybrid children, both have extremely wealthy and famous fathers, and both have participated in World Tournaments. Also black hair.
Fact: Videl is the fourth best Dragon Ball girl.