ISO = film speed (ie; 200, 400, 800, 1600) will a film camera you had to actually change the roll of film to get a different ISO, with digital there is an option with the camera that makes this adjustment within the computer chip of the camera to acheive the same thing.
Shutter Speed = mechanism to allow light into the camera for a specific length of time (2 seconds, 1 sec, 1/4th sec, 1/15th, 1/30th, 1/60th, 1/100th, 1/500th, 1/1000th, etc...)
Aperture (aka: f/stop) = the pupil of the lens. Works just like the pupil of your eye. Numbers are in fraction form therefor the smaller the number the bigger the hole. f/1.8 is a bigger hole than f/5.6 which is bigger than f/16, etc... This is where you can control the depth of field (DOF). If you want the subject in focus and the background out of focus (shallow DOF) then use a big hole (f/1.8-f/4), if you want the subject and the background to be IN focus, then use a smaller hole (f/16-f/22).
The combination of the ISO, Shutter Speed and f/stop gets you the final result. There are many different combinations and it does take some time to get the hang of everything
Shutter lag is how long it takes from you pressing the shutter release button to when the camera actually takes the picture. On the lesser expensive P&S camera's this will typically be a long time, upwards of well over a second or 2 in some cases. With most dSLR's, this will typically be a very short time, as fast as .2 or .4 seconds (almost instantly). There are some dSLR's that take longer than others and some P&S camera's that are much faster (very close to dSLR's) than others.
Almost all camera's (some of the very expensive dSLR's don't fit this description) have the option of point and shoot. Actually its point, focus and shoot. The camera has an AUTO function and will set everything (ISO, shutter & aperture) based on the readingn it gets from the light available where you are pointing the camera. All camera's also allow options where you make some of these choices or all of the choices.
There are many on-line tutorials and books available to help get someone through all the info. Canon has an on-line tutorial that is pretty good, I think there are a few online photography schools that have some free stuff. Some books like Digital Camera's for Dummies (or any of the Dummies books that relate to camera's) and Understanding Exposure are recommended a lot along with a few others (check out
amazon or barnes and noble).