Charlemagne’s name is really Charles le Magne, or Charles the Great. In German they call him Karl der Grosse, which also means Charles the Great. His father, Pippin, left Charlemagne his Frankish empire when he died in 768 AD. The Franks were already very powerful when Pippin died, but Charlemagne made them more powerful still.
To begin with, Charlemagne organized a centralized system of governors (counts) throughout his kingdom, sending out men he knew to keep order all over his kingdom, and then sending out other men to check up on the counts.
At the same time, Charlemagne also greatly expanded the size of his kingdom. He conquered France down to the Pyrenees mountains, and even into northern Spain. He crossed the Rhine river and conquered Germany, Switzerland and Austria, even into modern Hungary.
To the north, he conquered Belgium. And in 774 AD Charlemagne also conquered the Lombards in northern Italy. In 778, Charlemagne led a successful raid into Islamic Spain to capture Indian steel swords. Then about 800 AD he conquered the Avars. Charlemagne brought back so many Slavic prisoners to sell as slaves that people in his empire began to use the word “Slav” to mean slave, instead of the older Latin word “servus”, which started to mean “servant” as it does today.
From his position in northern Italy, Charlemagne was able to help out the Popes, who could no longer count on getting help from the Roman Empire. In exchange, Charlemagne got Pope Leo III in Rome to name him Holy Roman Emperor. Right at that moment (in 800 AD) the Roman Emperor in Constantinople was Irene, and the Franks refused to recognize Irene as Emperor because she was a woman. Charlemagne had offered to marry Irene, to put a man back on the throne and unite the old Roman Empire back into one Empire. But the Byzantines refused, thinking that Charlemagne was some barbarian nobody from northern Europe.
Along with his new identity as Emperor, Charlemagne built up a real court at his palace in Aachen, with a palace school, and new buildings being built everywhere, and books being written, including a biography of Charlemagne by Einhard which is modelled on the Roman biographer Suetonius. Charlemagne sent ambassadors back and forth to the Abbasid caliph, Harun al-Rashid, who sent him an Indian elephant as a present.
Learn by doing: make a clay statue of a person on a horse
More about the Carolingians