These are used to see more clearly things that are very small. Sometimes it is very important to be able to see these small things. Germs are very small but they can cause people to be very sick. It is important to be able to see which germ is causing the sickness so that the right medicine may be given. These are used to see things which are far away.
Large telescopes can look at things way out in space.
Smaller telescopes such as binoculars can make things look closer that are across a field from you. Binoculars used to be very important in war. The one using the binoculars could see the enemy coming when they were still far away. This gave them time to prepare to battle the enemy. The word mark is the Greek word for scope.