When BugSeeker is stopped at a line of code, the Debug | Step Into command moves the execution point to the first line of any method that may have been called on the current line. If there are no method calls on the current line, Step Into moves the execution point to the next line, which is the same thing that Step Over would do.
Use the Step Into command when you need to follow the execution path into any method call that have been made because you suspect the bug may lie within the method called or you wish to trace through that method's code.