Yea sure proto indo european since europe and india are neighbours w. nothing but places to debauch/mutilate and get cheap oil from, in the middle. Or Mesopotamia, another fictional made up word that was never a name of anyplace connected to reality. I guess those in the world/West who r proud of skintones and aggressive terizing others or colonizing & theft would rather let their Saudi "allies" bleed their own citizens and children or eat from toilet bowls than accept that Iran, a place that still exists as 1/5th the size it was long ago, was/is the source of 70% of world languages today since that would be so offensive to the Western and World's losers, who would do anything to belittle anyone to get things they want including rights, respect, & credit or material rewards, that may be associated w. others besides them. Although I would never go to such ridiculous lengths and distances to ruin any nation or culture by renaming everything decent about them into other fictional names just to belittle and degrade them and any small or big positive aspect, feature, or past/present achievement(s) they may have!
PIE is not the source of 70% of the languages or of the native speakers of given languages. There are abut 445 living IE languages, whereas there are about 6,500 spoken languages (plus some hundred or three sign languages). About 46% of the world speaks an Indo-European language as the native language.
The difference is a gender.
"мой" is masculine, "моя" is feminine, "моё" is neuter. And "мои" is plural form.
мой муж, мой сын, мой дом - my husband, my son, my house.
моя жена, моя дочь, моя жизнь - my wife, my daughter, my life
моё слово, моё мнение, моё решение - my word, my opinion, my decision.
мои дома, мои дочери, мои слова - my houses, my daughters, my words
Домой answers the question "where to?" (куда?) and implies moving towards home. I guess your friends are saying "Иду домой" (I'm going home) or "Идём домой" (We're going home/Let's go home). There is also "дома" (with the first syllable stressed) that answers the question "where?" (где?) and means "at home". Hope that helps.
The one time I have seen it used it with verbs of motion when my Russian instructor changed my sentence from "Я должна поехать дома" to "Я должна поехать домой" (sentence roughly translating to: I must go -by transport- to my house." We haven't yet gone over verbs of motion (i jsut like looking ahead) but I believe that is where it is used.
The way this guy teach Cyrillic is awesome if on Android