What is an off beat rhythm?

In music, an off-beat rhythm occurs when accents land on or after a weak rhythmic pulse or upbeat rather than on more typical strong-beat emphases. This kind of syncopated rhythmic pattern provides the music with interest and movement; and is the main rhythmic characteristic of styles and genres such as ragtime, swing, jazz, funk, soul, hip hop, reggae, soca, calypso, cumbia, son, salsa, etc. This sort of syncopation contrasts to, e.g., march rhythm:

March rhythm with steady beat:

1 2 3 4 | 1 2 3 4