English is a West Germanic language that was first spoken in early medieval England and is now a global lingua franca. It is an official language of almost 60 sovereign states, most notably the United Kingdom, the United States, Canada, Australia, Ireland, New Zealand and a number of Caribbean nations. It is the third-most-common native language in the world, after Mandarin and Spanish. Moreover, it is widely learned as a second language and is an official language of the European Union and of the United Nations, as well as of many other world organisations. English is spoken as a first language by around 375 million people.
Following the extensive influence of England, Great Britain, and the United Kingdom from the 17th to mid-20th centuries through the British Empire, and through the spread of English literature, world media networks such as the BBC, the American film and television industry, and the internet, English has become the leading language of international discourse and the lingua franca in many regions. As a consequence, more than a billion people speak English as a second language to at least a basic level.
Map of English speaking countries (source: Wikipedia)
Historically, English originated from the fusion of closely related dialects, now collectively termed Old English, which were brought to the eastern coast of Great Britain by Germanic settlers by the 5th century. After the Norman conquest of England in the 11th century gave rise to heavy borrowings from Norman French. In addition, a significant number of English terms originated from Latin. Last but not least, because of the assimilation of words from many other languages throughout history, modern English contains a very large vocabulary, with complex and irregular spelling
The best way to learn English, as much as any language, is by total immersion. Unfortunately, it is not always possible to spend a longer period of time in an English speaking country. However, you can start your immersion already now with vocabulary stickers.
Also, you can start to try to read English newspapers or you can watch some English TV or movies and listen to English music in order to assimilate a language immersion. Enrolling in a language course is the next best thing. Once you feel a bit more familiar with the language, a visit to the UK or USA will help you enormously to get the feel for the language.