The BOM is a Table Annotation that automatically is filled with information from your Assembly such as the Component Name, Number of instances and Description
Menu Bar→Insert→Tables→BOM
Command Manager→Tables→BOM
Balloon Annotations may be added to indicate which component matches on the BOM
Auto Balloon will attempt to automatically Balloon each Component, but this doesn't always work as intended
Use the Magnetic Line Tool to make all the Balloons appear in a straight line