Documentation for other versions: amCharts 4 (current) or amCharts 3.
AmBalloon is the class which generates balloons (datatips). Balloon follows the mouse when you roll-over the pie slice/line bullet/column/etc, chart indicator of serial charts displays value balloons and category balloon. Balloon instance is created by the chart automatically and can be accessed via "balloon" property of AmChart. Chart shows/hides and sets position for every balloon automatically, so all you need to do is to change balloon appearance, if you want to. For example:
chart = new AmCharts.AmSerialChart(); // get balloon intance var balloon = chart.balloon; // set properties balloon.adjustBorderColor = true; balloon.color = "#000000"; balloon.cornerRadius = 5; balloon.fillColor = "#FFFFFF";