Imperialism is considered a phenomenon of the nineteenth century, although it began long before. Imperialism is the expansion of one country into another.
England, in the 19th century, had a very strong navy. It was able to defeat most other countries, even Spain, which had the famous Spanish Armada. It also expanded into places such as India.
In France Charles X sent French troops into Algeria in 1830, and there they stayed until 1962.
Russia either annexed or conquered many countries, among them Georgia, Armenia and Azerbaijan. In the 1860’s Russia invaded Turkestan.
China at that time was very weak. When the East India Company started importing opium the Chinese were powerless to stop them. The First Opium War (1839-1842) was followed soon after by a second, in which the British gained many rights on Chinese soil.
Africa was the main place where everyone was congregating to grab territory. Belgium’s king, Leopold I, went to Congo, where he treated the people brutally, exterminating almost half the population. Britain focused on Egypt and South Africa, while other powers tried to grab all the territory they could.
Interestingly enough, Ethiopia and Liberia stayed untouched during this rush for new land.
In Asia the Dutch occupied Indonesia, the French Indochina, and the British settled in Burma.
China, meanwhile, had grown sick of foreigners. It tried uprising but against the British and French flood, none succeeded. It was too weak to do anything.
Japan, on the other hand, was very strong. It controlled China and it was also expanding elsewhere.
The Boer War was between the Dutch (already settled) and the British (invading) over South Africa. There were very cruel concentration camps on the part of the British. Some 20,000 of the original 120,000 Dutchmen who were taken prisoners and put in the camps died.
In the Russo-Japanese War (1904-1905) it was the Japanese who were eventually victorious. This was very shocking to the Europeans, that such a so-far-insignificant country could have suddenly become so powerful.
This is the basic imperialism of most of the major countries of the world.