The weekend is the two days at the end of the week: Saturday and Sunday. Many people do not work on the weekend, and schools are closed on the weekends.
Welding is a process for joining two pieces of metal together. Welding creates enough heat on the join to melt the edges of the pieces of metal being welded, as well as adding a filler metal into the join. Welded joints are extremely strong.
A well is a deep hole that has been dug into the ground to reach water. You can use a bucket on the end of a piece of rope to get to the water, or you can use a pump or windmill to suck the water out.