Hole

Hole command in each option brings different operation.

The [Highlight holes] check is active, opening edges are highlighted.

Fill up

It fills a hole up by mouseclicking an edge of a hole. A current material is assigned to the new face.

Original   A color of an edge is changed
when the mouse cursor is over it.		   Fill a hole up by clicking
(Polygon option is active in this picture)

You can select an option to fill up.

Center vertex
ON		 Triangulate
ON
A vertex is put at the center. Divide into triangles.

Bridge

It makes faces to connect two holes by mouseclicking them.

The new faces are created in the current object, and the current material is assigned to them.

Original (Left: hole A, Right: hole B)   An edge around the hole A are highlighted when the mouse cursor is over it.   The hole A is selected by clicking.  
 
An edge around the hole B are highlighted when the mouse cursor is over it.   A dialog is opened and a preview of a bridge is shown after clicking a hole B.   A bridge is created after pushing the OK button.  

After two holes are selected, the following dialog is opened.

Segment
It specifies a number of a division of a bridge.
Segment : 2 Segment : 10
Tension
It specifies a tension for a bridge. A larger value makes a more expanded shape.
Tension : 0.00 Tension : 0.50
Rotate
It rotates a bridge. When you click the left button or the right button, a pair of vertices between a bridge are switched.
No rotation Rotate left once

A bridge can be made even if shapes or size of holes are different each other.