A map is a drawing. It shows what it looks like on a part of the earth. However, there are not only maps of the earth, but also of other planets and moons: a map of the moon, a map of Mars and so on. A map of an ocean is a nautical chart.
Anyone who makes a map is a cartographer. The science of this is called cartography. First you have to know what an area looks like: For example, what roads and rivers there are, whether there are houses or even towns there, whether some areas of land are higher than others.
Then you draw the map. In the process, many things are described more simply than they are in reality. A river is a thin blue line on the map. In fact, not all rivers are blue, and they are not all the same width. But it is easy for the reader of the map to immediately recognise a blue line as a river.
It is important to know what scale a map is. After all, the map cannot be the same size as the country it describes. For example, if a map has a scale of 1:10,000, this means that what is 1 centimetre long on the map is actually 10,000 centimetres, i.e. 100 metres long. You also look at the compass direction. On most maps, north is at the top, south at the bottom, west at the left and east at the right. A book with many maps is also called an atlas.