Firstly, the "B" represents borders. Borders are important because it defines the edges of the area.
Secondly, the "O" represents Orientation. Orientation is also important because we need to find the direction.
Thirdly, the "L" represents Legend. Legend is very important in a map because it shows what that place is.
Fourthly, "T" represents Title. Title is important because it shows what type of map it is and what place or country it is. For an example, there are political maps, road maps, climate maps, physical maps, and resource maps.
Finally, the "S" represents Scale. Scale is an important element because it shows the real length between two places by measuring the length between two places in a map.