You have seen tall mountains in real life or in a book. You have probably listened to weather reports too. A weather report for mountains may tell you to plan for a warm spring rain. Or, this report may tell you that there will be heavy snow that day.
Temperatures often change with the height of a mountain. Some people get reports for various locations on the mountain. A valley might have warm temperatures and rain showers during the day. On the same day, higher places might have cold and heavy snow.
Plants and animals begin to change with different mountain heights too. Pines grow at lower levels of the Rocky Mountains. Higher in the mountains, firs and spruces appear. Bears, deer, elk, and many other kinds of animals live among the trees. On mountains there often is a very distinct height above which trees do not grow. Goats and sheep eat the grasses and other small plants that grow there.