From the creation of States as a nation, they all felt the need to establish borders, promoting separation between countries so that there was no intervention of sovereignty, that is, so that a country would not try to enter the territory neighbor.
The boundaries between territories aim to identify where one territory begins and another ends. All territorial limits existing on the face of the Earth were established through agreements and treaties between the countries involved. After this process, imaginary lines were implemented, which are, in large cases, marked by means of natural elements such as rivers, lakes, mountains and mountains or a construction of an artificial frame over the ground.
The expression limit is often confused with border, however, this corresponds to the entire length of the border line of a country (example border between Argentina and Brazil). Every country that has a coastline holds part of the territory in marine areas up to a certain point in the ocean, called the maritime boundary.
Zones close to borders between two nations are normally urbanized and produce a great commercial and cultural flow between inhabitants of the nationalities involved.
A large number of countries have a defense scheme in the border strips on the continent and at sea, in order to protect the territory and preserve sovereignty, in addition to preventing the entry of contraband, drugs, weapons, illegal immigrants, between others.
By Eduardo de Freitas
Graduated in Geography
Source: Brazil School - https://brasilescola.uol.com.br/brasil/as-fronteiras-brasil.htm