Upbeats, anacrusis or pickups are the same thing: they all refer to the weak beat (or beats) that lead into a strong downbeat. Basically, they are used to describe a note or group of notes that occur before the first strong beat (downbeat) of a phrase or measure.
Here are some examples of upbeats, anacrusis or pickups:
The following instead, are not upbeats, but regular bars:
In other words, you can easily recognize an upbeat (anacrusis, or pickup) if the total value of the notes in the first bar is smaller than the full measure’s time signature.
Improve your piano playing with our video lessons. Presented by top-notch music teachers, our structured video lessons, you'll gain the skills and confidence needed to play with precision and artistry.