Shutter speeds are the controls that allow how much time film is exposed to light. The way it worked in film cameras was there were usually two cloth curtains were attached to the back of the camera. Think of the curtains of your window. When you pushed the button to take a photo, depending on how long your speed is, one curtain would start to move, and it would open up and let some light in through the crack.... and after a certain amount of time, the other curtain would start to follow and close the crack... if you have a fast shutter speed, the second curtain follows the first pretty quickly and has a small light opening... if you have a slow shutter, the gap would be bigger and more light would be allowed through..
Digital cameras dont have curtains. They just have a sensor that acts like one. Some cameras have what are called sync speeds.. that means when a flash goes off, if you are using a high shutter speed, then the only part of your image that is properly exposed is the gap between the curtains at the time... the slower the speed, the bigger the gap, the more the flash can expose. Usually you would find this out when you photographed something and half the photo on the left was dark, half on the right was dark, but right down the middle was a nice image, but only about 20 % of the image was recorded, the rest was underexposed.
Most digital cameras have pretty high sync speeds, but it used to be you could not take an image with a flash with a speed of 1/60 or faster.
Speeds are thus... kinda .. 1 second, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500. Some cameras can do slower, faster, in between, but these are what we're using now. Notice again that each is 1/2 to twice as much as the one next to it. Sorta... Mathmatically it worked out, but youre just gonna have to trust me on this one.
Since most of these are fractions of a second, your image is exposed pretty quickly.. The faster ones do the nifty things, like freeze a bird flying, cars on the highway, etc. THe slow ones do things like water flows in a water fall, speed blurs, timed exposures of stars etc.
Well... since pretty much what a woodworker wants to shoot is not moving all that much, why care?
It's one of the units we need to know that IF we change one of the others, THis MIGHT be one of the ones we have to change.
General rule of thumb. I was taught that anything slower than 1/60th should be mounted on a tripod. Your breathing, heartbeat, a train, etc could cause vibrations that would blur your image. And we dont like blurry images unless we did it intentionally.