Portuguese is the fifth most popular language in the world, spoken natively by over 190 million in 8 independent countries (Portugal, Brazil, Angola, Cape Verde, Guinea-Bissau, Mozambique, São Tomé and Principe, and East Timor) and several other former Portuguese commercial outposts in India (Goa), China (Macao), some islands in the Atlantic which are still Portuguese territories, as well as modern-day migrant communities in many countries.

Portuguese is a direct descendent of Galego-Portuguese, the language of the Galicia region. By the end of the Roman Empire, the Iberian Peninsula had adopted Latin (or Vulgar Latin to be more exact) as its official language (well, except for the Basques). Between the 5th and the 7th century, many different languages sprung, derived from Latin and smaller, local languages. A few centuries later, however, the Arabs would have invaded nearly half of the peninsula. With the sanction and support of the Church, many noble men from all of Europe were called to fight against the Arabs.

One of them was Dom Henrique, duke of Burgundy, who became the ruler of part of Galicia in 1096 as a recognition by the king of León and Castile for his many military successes. His son, Dom Afonso Henriques, is recognized as the first king of Portugal, thus beginning the lineage that would be ruler of the first Modern National State. This family successfully regained control of the territories south of Galicia, expanding their territory to more or less what Portugal is today.

Galego-Portuguese was an important cultural language. It crossed boundaries, being a literary language also in the kingdoms of Castile and Leon and influencing nearly all of what is today the north of Spain. This ancient language is the common ancestor of both Portuguese and modern-day Galego (= Galician). During the Middle Ages, its main sources of influence were Provençal (whose poetry was very well accepted in Portugal) and Castilan. Latin was already the basis of Portuguese, but it was during the Renaissance that the language was consciously brought closer to Latin by those who were given the responsibility to write its first grammars. If there was an ambiguity in common usage, the linguists of the time would choose the form that was closer to Latin - it all depended on who scored more points in the "proximity to Latin index". Many unexplainable and excessive rules that were forced down people's throats came from this conscious Latinization of the language as well as from the failed theories of the time that identified Portuguese as a superior language and attempted to "speed up" its development by artificially amending the language to what was thought to be its natural course of evolution.

Around this time, Portugal was a strong, wealthy country. They found the first maritime route to India, started creating outposts in Africa and Asia, and found South America. There's very little left information left, but almost certainly Portugal and Spain were well aware of America before Christopher Columbus reached it, as some political choices at the time by both countries show. There was high secrecy around the navigations, and the truth will probably never be known.

The most important Portuguese colonies largely maintained the language at least as an official language, even if there are smaller tribal languages in Portuguese-speaking African countries. Brazil is the largest Portuguese-speaking country, and it has largely abandoned its native languages (something which was achieved by violence, as the Portuguese outlawed all native languages after the second half of the 18th century). Native indian languages are spoken today only in the few indian areas that are left, most languages being known, but not actively used, by groups that are rarely larger than a hundred persons, most of the time as an effort in preserving their existence rather than a sign of their usefulness in the modern world. Macao has adopted Chinese as its first language when it was given back to China. East Timor lived under Indonesian rule for a long time, and Portuguese is not as established as its "official" status might indicate. Both Portugal and Brazil are sending teachers and linguists to aid in making Portuguese East Timor's national language.

All of the Portuguese-speaking countries and territories share a reasonably common written language. The norm in all countries draws heavily from the Portuguese norm, but actual practice, even in formal and official contexts, is more relaxed. Portuguese speakers can slow down and adapt their speech to make themselves understood by Portuguese-speaking foreigners, but that's a bit difficult at times and requires training. Native Indian and African loan-words in Brazil and African loan-words in Africa further complicate the issue. From my point of view (I'm Brazilian), the Portuguese have a tendency to ignore all vowels in their speech, and there are marked differences in rhythm. Specific areas of interest, in particular recent specific areas of interest often have widely different vocabularies. Brazilian Portuguese accepts English loan words more easily than European Portuguese, which favors a translation or, as a second option, French. Thus I'm using a "mouse" in Brazil, but a "rato" (literally a mouse) in Portugal. Same goes for the "monitor" against "écran", etc.