Although it was danced from the early 1900s, the Charleston is generally associated with the 1920s, ‘flappers‘, and speakeasies. The dance appeared in several stage shows, but only became a big hit with ‘Running Wild’ (1923), which contained the song ‘The Charleston’, composed by James P. Johnson.
The dance is characterised by its distinctive, energetic, toes-in, heels-out, flicking footwork. The Charleston can be danced both with a partner, in an upright, traditional ballroom hold, or solo (most often by women) with relaxed posture and swinging arms.
The Charleston is normally danced to ragtime jazz, a faster precursor to the swing jazz associated with Lindy Hop. The Charleston’s moves fed into Lindy Hop’s development in the 1930s, evolving into the later ‘swinging Charleston’, ’30s Charleston’, or ‘Lindy Charleston’ (which is the first step we cover in our beginners’ course).
For much more information check out Wikipedia’s page on the Charleston.