If you play a figure "straight" ... the spacing between the notes are exactly equal.
Example ... play eighth-notes ... when played straight, each note's duration is equal to the next, so the space between each of these notes is also equal.
If you
swing the eighth-notes, the note duration and space is no longer equal from note to note. In the case of a series of swung eighth-notes, the notes on the down beats (1 2 3 4) are going to have a longer duration because the upbeat eighth-notes are delayed, and now have a shorter duration.
Often times swung eighth-notes are thought to be like triplets with the middle note missing ... and sounds like
Do0-bah Doo-bah, etc. This is just one example. And swinging a figure does NOT mean that it has to fit within the triplet regime.
Straight is going to sound like your metronome.
Swung is going to have a lilt to it ... some may say shuffle ... with the first note being long, the second note being short, and so on.
Some may say that anything that isn't straight is automatically considered to be swung/swing.
