Kiruv is a Hebrew word that means "bringing close," and can mean any form of bringing someone or something close—physically, emotionally, or spiritually. With regards to other people, kiruv is the fulfillment of the biblical obligation to "Love your fellow as yourself."
The term is commonly used in reference to Jewish outreach, which is aimed at bringing other Jews closer to G‑d and their Jewish heritage. Out of love for your friends, you share with them the beauty of the Torah and its precepts, knowledge that you are lucky enough to be privy to.
Although encouraging fellow Jews to strengthen their commitment to Judaism has always been a Jewish value, this concept has reached new dimensions in the last sixty years, and has become what is referred to by many as the "Kiruv Movement."
The upheaval created by two world wars, and specifically the destruction of the religious Eastern European Jewish communities, left a societal split in the Jewish community, with a historically unparalleled trend leaving many Jews estranged to the teaching and traditions of their ancestors. Sensing that this was the call of the hour, the sixth Rebbe of Chabad-Lubavitch, Rabbi Yosef Yitzchak Schneersohn (1880-1950), started the idea of organized Jewish outreach. Disregarding both the counsel of well-intentioned friends as well as the ridicule of antagonists, he encouraged his followers, young and old, to dedicate their lives to reversing the erosion of Torah life in the Jewish community.
This idea was cultivated by Rabbi Yosef Yitzchak's son-in-law and successor, Rabbi Menachem M. Schneerson of Lubavitch. Teaching that no Jew is "secular," and that the Torah is the birthright of every Jewish soul, the Rebbe, through his shluchim, or emissaries, founded educational centers for Jews of all ages, and brought mitzvot to the streets and to the homes of Jews of all backgrounds and affiliations. Currently, there are more than 3000 Chabad Centers around the world, all devoted to advancing this goal.
With the passage of years, this approach was, thank G‑d, adopted by many segments of the Jewish community, and the outreach attitude has now become all but universal.
To conclude, R. Aizik Homiler, a venerated chassid of the first three Chabad-Lubavitch Rebbes, would relate an oft-repeated adage he had heard from older chassidim:
Have affection for a fellow Jew and G‑d will have affection for you.
Do a kindness for a fellow Jew and G‑d will do a kindness for you.
Befriend a fellow Jew and G‑d will befriend you.
Rabbi Baruch S. Davidson