As far as the compiler is concerned, there is no difference. As far as the programmer is concerned doc comments begin with /** and regular comments begin with /*. Doc comments are automatically parsed out by javadoc.
/**
 * This class represents a node of a binary tree.
 * @version 1.0 of August 26, 1996 
 * @author Elliotte Rusty Harold 
 */
public class treenode {
  double data;
  treenode left;
  treenode right;
  /**
   * Creates a new node with the value d
   * @param d The number to be stored in the node
   */
  public treenode (double d) {
    data = d;
    left = null;
    right = null;
  }
  
  /**
   * This method stores a double in the tree by adding a new node
   * with the value d below the current node.
   * @param d The number to be stored in the tree
   */
  public void store (double d) {
    if (d <= data) {
      if (left == null) left = new treenode(d);
      else left.store(d);
    }
    else {
      if (right == null) right = new treenode(d);
      else right.store(d);
    }
  }
  
   /**
   * This method prints this node on System.out.
   */
  public void print() {
  
    if (left != null) left.print();
    System.out.println(data);
    if (right != null) right.print();
  
  }
  
}