i think this refers to a method known as hyper-focal distances. i'm not too sure, but basically i think this is how it works:-

every lens for a given aperture will have a distance which the subject matter will be sharp, so long as it is within the distance range (depth of field). where you want to get as MUCH in focus as you can then if you set the focus to infinity then you have wasted some of the focal distance. i've just checked on a 35mm lens i have, which says on the lens that if the focus point is 3m and i have a f22 aperture, then infinity will also be in focus. the good news is that at 3m focus point, then anything beyond 1m will also be in focus. if i let the camera focus on infinity then my lens tells me that anything closer than 3 m will be out of focus. so in this case, i gain an extra 2m of focusing distance close to the camera by not letting the camera focus on infinity, which is great if i had a flower / or rock really close but also wanted the distance sharp too. so if i wanted as much as possible to be in focus i would be better to manually set the lens to 3m, f22, knowing that infinity would be in focus.

make sense? it gets a bit complex

bean bag - yes, anything that helps you steady the camera will help. bean-bags tend to be used with long focal lens, as resting these on a bean bag takes the strain and helps to keep steady. not too sure i've heard of people using them with short-lens. note- this only helps

sun - same applies with your eyes. don't look at sun if in full glare, but when low or behind clouds, trees then okay but be careful if it suddenly comes out. the difference to be aware between your eyes and the camera, is that the lens will magnify the effect, so take care if in doubt.

hope that helps and best wishes,