The single most important sense is the literary one:
白话文 (báihuàwén) is 'vernacular writing' — Chinese written the way people actually speak, as opposed to
文言文 (wényánwén, Classical Chinese).
鲁迅's 1918 short story 《
狂人日记》 (A Madman's Diary) is the landmark work that established
白话 as the basis of modern Chinese literature.