A stepwise progression is a chord progression that moves in whole or half-step intervals along a musical scale. Typically considered a no-no by most musicians and composers and is usually thought of as a beginner's mistake in writing music. Coincidentally, many ancient and medieval songs utilize them as well.
However, it many stepwise progressions are used not only in many popular songs but even some very common progressions (the I - ii - V - i or I - IV - V for example).
For some strange reason, it tends to sound much better in the minor key. Common modes to utilize it include the Mixolydian (VII - I) and Phrygian (i - II).
Some songs that use stepwise progressions: