The world being as it is today with so many countries issuing plenty of stamps each year, it is completely impossible to get a complete collection of the entire world. One has to specialize in a country or a few countries or for example a group of countries as Latin America, British Colonies, French Colonies, Scandinavia or whatever one prefers. One can also choose a certain topic and disregard the countries and only collect stamps that have pictures that one likes. One can collect stamps that have pictures of animals on them or pictures of ships, trains, birds, horses, Olympic themes etc. Stamp collecting certainly is an exiting hobby and people of all kinds have collected stamps like the British Royalty, King Farouk of Egypt, President Roosevelt and many other prominent people.
Stamp collecting is also highly educational.
One learns about foreign money, foreign countries, history, art etc. and stamps do not loose their value. In fact they have international value and can generally be brought in and out. Some people ask if these stamp collections contain mint stamps or used stamps. Mint means un-used. Well, they mostly consist of both, some are mint and some are used.