You can configure how Amarok transitions from one song to the next.

No Crossfading: provides a silent gap between tracks, specified in milliseconds.

Crossfading: provides a nice fading effect. The crossfade period is also specified in milliseconds.

The remaining checkbox configures the the following option:

Resume playback on start allows resuming playback of the last track that was playing when Amarok was closed, from the last known position in the track.