"Said Hufflepuff, 'I'll teach the lot,
And treat them just the same.'"
-- Sorting Hat (OP11)
Helga Hufflepuff was the founder of Hufflepuff House and one of the co-founders of Hogwarts, described as one of “the four greatest witches and wizards of the age” (along with the other three founders) (CS9).
She was much more accepting than the other founders, advocating for accepting all students and treating them all equally. Hufflepuff House continues to be notable for those traits that Helga Hufflepuff herself prized: fairness, loyalty, and hard work.
According to the Sorting Hat, Hufflepuff came “from valley broad” (GF12), which possibly indicates Wales. She was the one to first employ a contingent of house-elves in the Hogwarts kitchens, giving house-elves a safe home and benevolent master (PC/JKR1).
Her Famous Wizard card states that "[s]he brought people from different walks of life together to help build Hogwarts and was loved for her charming ways" (FW).
As noted above, the Sorting Hat clued us into Helga's origins in "valley broad," and most likely the region of Wales. On Mugglenet's podcast Alohomora! during discussion of Goblet of Fire, commenters theorized that this "valley broad" connection may also reflect Helga's associations with food, sustenance in general, and agriculture in the fertile valleys of Wales. This may also reflect general fertility associations related to feasting and the productivity of the land. Her associations with the Hogwarts greenhouses and gardens highlights the agricultural associations as well. Helga may have also been a robust woman and so may be accurately described as a "valley broad" herself. --Hufflepuffskein