You can’t make any big statements that describe all of Mongolia.
80% of Mongolia’s land is open grassland, but half of Mongolia’s 3 1/2 million people live in Ulaanbaatar, the capital city. So one big contrast is between a large city full of activity and areas covered with a lot of grazing animals and not very many people.
Ulaanbaatar is a large modern city surrounded on three sides by the ger district, an area in which there are many kinds of buildings including the same gers that you find in the countryside.
You can see mountain ranges throughout Mongolia, with the highest being the Altai Mountains in the southwest part of the country. These areas are cool even in summer, and get very cold during the winter. They are a big contrast with the Gobi Desert area, which is dry and sandy with extreme swings of temperature from -40° centigrade (-40° fahrenheit) in winter to over 45° centigrade (over 100° fahrenheit) in summer. (Notice that at -40° centigrade and fahrenheit are the same.) There can be temperature swings of over 30° centigrade (60° fahrenheit) in a day!
In mountainous areas you also find trees, which are rare in the steppes and in the desert. People use those trees to build structures that you might find unexpected: Here is an example. If you are from the United States it probably looks familiar!
Lake Khuvsgul, in Northern Mongolia, is Mongolia’s largest freshwater lake: clear and vibrantly blue. Much of Mongolia is very dry during most of the year, a contrast with this green, lush area.
There are some big paved roads and trains, but in the countryside, much of the time if you are driving it is on dirt paths or even just car tracks through the grasslands. When you are driving on these roads, the driver has to be incredibly alert because there are bumps, holes, and bends that can get you into some deep trouble it you aren’t watching!