People use the terms interchangeably. They are both technically called "Serigraphy".
"SILK screen" it was called because the screens were originally made of silk fabric. Later, synthetic materials were used and silk was no longer part of the process therefore just 'Screen" printing after that.
The process uses low-viscosity ink, not paint. The light you speak of is used for 2 parts of the process - now this is going back to the 90s when I was in college for my Bachelor's in print tech and Print mgt. - first, the screen is stretched across a frame (just like you'd secure a new screen on a screen door). A liquid emulsion is mixed and applied to the screen (in college is was really icky green-colored stuff). The emulsion dries then you attach the negative or positive in the proper place to the coated screen, expose it to UV light. The exposed portion hardens and the unexposed portion does not. You rinse away the unexposed portion. Then you place the screen on a substrate - paper, shirt, jacket, etc - and you squeegee the proper color ink through the screen. The ink goes through the rinsed-away areas creating an image on the substrate. After the screen is lifted, the ink is usually cured with UV Light to make it fast and Voila!, you're done - or you add the next color.
In college, this was GREAT FUN - I loved it and my projects usually consisted of many, many colors. I did two projects for friends in school. One was red jackets with metallic ink image on the back for a friend who owned a car restoration shop. The other was for a very good friend of mine who raced Arabian horses - she drew a picture of about 8 colors and I silk screened this on a bunch of pink satin jackets. It looked really cool!.
Hope this answers your question
No.. they may look similar but, one is for moving water and the other is used for moving ink. The silk screening squeegee has a rounded edge and is firm where as a window squeegee tapers and is more flexible. I mean just think of the difference between water and printing ink.