Although the concept of Indo-European is primarily a linguistic one, it is none the less clear that merely by postulating the existence of this language we have also to postulate the existence of a homogeneous group of speakers characterized by a particular culture, as is the case with any natural language. Indo-European formed an essential part of that culture and was to some extent a faithful reflection of it. This observation has many repercussions from historical and sociological perspectives.
Words derived from the Common Indo-European language are preserved in a large number of languages: numerals from one to ten; the word meaning the sum of ten tens (Latin "centum," Avestan "satem," English "hundred"); words for certain bodily parts (heart, lung, head, foot); words for certain natural phenomena (air, night, star, snow, sun, moon, mind); certain plant and animal names (beech, corn, wolf, bear); certain cultural terms (yoke, mead, weave, sew); monosyllables that pertain to sex and excretion (example: modern English "fart" likely derived from Indo-European "perd"; also modern English slang "f---" perhaps derived from Indo-European "peig" or "pu" meaning respectively "hostile, evil-minded" and "to soil, defile").
Indo-European is merely one of hundreds of known language families, and PIE was merely one of hundreds of languages (or more) spoken during the late Neolithic. PIE is therefore not the primeval ancestor of all languages now spoken, nor even of a majority of them (although there are more speakers of IE languages than of the languages of any other family). At the present time, we do not know whether any other language families share a common ancestor with PIE.
The nineteenth century also saw the creation of a name for the family, Indo-European or, in German-speaking lands, usually Indogermanisch 'Indo-Germanic'. The ancestor of all the IE languages is called Proto-Indo-European, or PIE for short. During the course of the nineteenth century, the methods of comparative linguistics and linguistic reconstruction were developed; a prodigious number of important discoveries in the watershed decade of the 1870's was responsible for significant refinement of the method and for firmly establishing historical linguistics as a science unto its own.
The Indo-European languages fall into two general branches. At some time in the distant past, the original Indo-European speakers migrated westward and eastward from a location north of the Middle East. We can trace those migrations by looking at vocabulary in each language, and gradually seeing the sound changes that took place over time as the tribes drifted further apart. The Indo-European tribes that migrated westward tended to pronounce words with hard /k/ sounds--a velar stop. On the other hand, those that migrated eastward pronounced similar words with /s/ or /sh/ sounds--a fricative sound. Likewise, the westward travelers tended to have certain vowel sounds transform into /e/ sounds while the eastward travelers tended to switch to /a/ sounds over time, and the labio-velar stops in westward traveling tribes tended to turn into velar sounds. Philologists have named the two branches Centum and Satem. Centum is the ancient word for "one hundred" in Latin, a language in the western branch of Indo-European. Satem is the ancient word for "one hundred" in Avestan, a language in the eastern branch of Indo-European. The two words illustrate the major changes in a single word as the Indo-European tribes drifted in two different general directions.
The Indo-European language family is made up of eleven subgroups, though one hastens to add that various scholars see the issue of subgrouping differently, especially on the question of Balto-Slavic, Italo-Celtic, and some of the peripheral languages such as Venetic and Illyrian.
The Anatolian family includes the oldest attested Indo-European languages: some Hittite documents are dated as early as the 18th century B.C. It is thought to have been the first branch of Indo-European to separate from PIE, and it was also the first branch [known to us] to become extinct, being replaced by Greek ca. 2nd/1st century B.C. Buried and lost until modern times, Hittite cuneiform tablets were first unearthed in the early 20th century in north-central Turkey, and helped revolutionize Indo-European linguistics. A sister language, Luwian, was probably spoken in Homer's Troy, located southwest of the Dardanelles.
It's speculated that the so called Kurgan were the original Indo-European people; lived northwest of the Caucasus, north of the Caspian Sea, as early as the fifth millennium B.C. Their language is known by scholars as Common Indo-European or Proto-Indo-European. Aspects of Kurgan culture: domesticated cattle and horses, farming, herding, four-wheeled wagons, mobility, mound builders, hilltop forts, complex sense of family relationship and organization; counting skills; used gold and silver; drank a honeybased alcoholic beverage, mead; multiple gods (worship of sky/thunder, sun, horse, boar, snake), belief in life after death, elaborate burials.
Today, the Indo-European languages have spread across large portions of the globe. They include diverse tongues like English, Russian, French, Latin, and Hindi. While English is very different from Hindi, for instance, they both come ultimately from the same source: Indo-European.
Indo-European is the name given for geographic reasons to the large and well-defined genetic family including most of the languages of Europe, past and present, and extending across Iran and Afghanistan to the northern half of the Indian subcontinent.