The conquest of England by the Normans began in 1066 with the battle of Hastings, where the English fought against the Normans. The conquest was complete in 1086.
Who were these Normans who conquered England ? They were Vikings or 'Norsemen', men from the North. Some 150 years before the conquest of England they came to a part of France, opposite England, a part which we now call Normandy.
What did the Norman Conquest do to England? It gave it French kings and nobles. The Normans also brought with them the French language. After the Norman Conquest there were three languages in England. There was Latin, the language of the church and the language in which all learned men wrote and spoke; the kings wrote their laws in Latin for some time after the Conquest. Then there was French, the language which the kings and nobles spoke and which many people wrote. Finally, there was the English language which remained the language of the masses of the people. Some men might know all these languages; many knew two; but most of the people knew only one. There were some people who understood the French language though they could not speak it. Rich people who owned land, the landowners, often knew French and Latin. But poor people, the peasants did not understand French or Latin. They understood only English.
In time, however, came the general use of the English language. About 1350 English became the language of law; and at that time lived the first teacher who taught his boys to read and write English and to translate, not from Latin into French, but from Latin into English. Then between 1350 and 1400 Wycliffe made the first complete translation of the Bible into English, and Chaucer, 'the Father of English poetry'.
But the English language when it came into general use was not quite the same as it was before the Conquest. The grammar remained, but many words came into it from the French language.