Sonatas, like symphonies, can be just as long to play and contain just as many movements, but they are generally played by only one or a few players. A sonatina is a baby sonata. It is still played by only one or a few players, but the length of the music is not as long, and there are noticeably fewer movements. When played during a concert, the soloist stands or sits in front of the rest of the orchestra on the stage. Oftentimes, classical concert-goers go to performances mainly to hear the concerto.
Some classical music is meant to be danced to.
Waltzes fall under this category. You can tell if a piece is a dance if it's repetitive and has a steady rhythm that you find yourself moving to. Serenades were basically created to be background music. Kings and other important people used to order for them to be played during dinner parties and other functions where it was good to have music involved but not to the point where they were the focus of the gathering. Most serenades last for about half an hour and are generally uncomplicated, mild, and soothing to listen to.