The Indo-European language family.

(click on above image to enlarge)

Being the largest family on Earth, the Indo-European (IE) language family has brought fascination and confusion to many people interested in this family.

A huge misconception that has spread over the decades (most likely propelled by Indian chauvinists) is that Sanskrit is the Proto-Indo-European (PIE) language from which arose the modern-day IE family of languages.

In reality, nobody knows the name of the PIE language. While Sanskrit is one of the most ancient IE languages spoken and the first known IE language to use a writing system, it is not the PIE.

Sanskrit is derived from Proto-Indo-Aryan, which in turn is derived from the Proto-Indo-Iranic language.
Sanskrit is the parent of all modern Indo-Aryan languages such as Punjabi, Sindhi, Urdu/Undri etc.

Another fact most people interested in the IE family are unaware of is that the closest living language to PIE according to linguists is Lithuanian. This is because unlike most IE languages of today, Lithuanian stayed mostly the same and changed very little grammatically.

According to a friend of mine who has a masters degree in linguistics, the closest language to PIE was Hittite, a language spoken in Anatolia, present-day Turkey.

Another widespread misconception promoted by Indian pseudo-scientists is that the IE family started in present-day India and spread out from there.
This is known as the "out of India theory," but only accepted by Indians and rejected elsewhere worldwide.

The IE family is actually traced back to it's early beginnings in the Black Sea region. Some linguists and historians claim that the PIE language can be traced back specifically to Southern Ukrainian regions of which many have been submerged by the Black Sea.
However, what is agreed upon by linguists and historians is that the IE family did start somewhere around the Black Sea region.

My best guess is the IE family was spoken in areas today submerged under the Black Sea.

From there the ancestors of most modern-day IE speaking peoples spread to the most Eastern and Western corners of Eurasia. Over time and geography, their languages slowly started to drift apart and slowly evolved into the modern-day IE languages as we know them today.

Depending on their geography, IE languages borrowed vocabulary from languages near them.
As an example, the IE languages spoken in Iran and Pakistan have a lot of Arabic and Turkic words in their vocabulary. This is due to their close proximity to Arab and Turkic speaking areas.

The furthermost east the ancient IE speaking peoples reached was the Altay mountain region and the Xiang province in present-day China.

According to a documentary I saw on the Tocharians, the Centum languages in the IE family are differentiated from Satem languages because Centum languages use certain suffixation and sounds that are absent in Satem languages.

The IE peoples that went westward evolved into modern-day Europeans. Most IE speaking peoples (not all) share common Haplogroups R1A and R1B

At one time ancient Indo-Europeans spanned throughout most of Central Asia but were later destroyed and/or assimilated by nomadic waves of Turanian peoples spreading out of the Altay mountain region.

A lot is to be learned about the PIE language and it's early successors. So far linguists have been able to reconstruct certain words based on modern IE languages and older ones such as Latin, Greek and Sanskrit.

But until they do, it would be wrong to assume anything and elevate it to "fact" without proof or even evidence.