The molecules pull on each other in every direction. When a liquid is enclosed in a container, like a glass, the molecules on the surface tend to be pulled back into the liquid or to the sides since there are no molecules above them. Thus, there is an increase in the attraction to the sides of the molecules. That is why you can fill a glass with water past the rim of the glass.
Surface tension keeps the water from spilling over.
The surface tension in the water is just too strong for the water film to stay intact as it stretches. Think about a piece of taffy - if you stretch it too far it breaks. Thus, to make a bubble we need to add to water some substance that decreases surface tension. Soap is an ideal substance because it is made of long chains of carbon and hydrogen atoms. This latter end likes to attach to grease.