Tikkun olam encompasses both the outer and the inner, both service to society by helping those in need and service to the Divine by liberating the spark within. As we are, the Divine spark lies hidden beneath our layers of egoistic self-centeredness. That spark is our conscience, through which the promptings of the Divine Will flow toward us. By pursuing spiritual inner work to strengthen our soul and purify our heart, we grow more able to bear that spark without shattering, more willing to act on what we know to be right, less willing to act in harmful or grasping ways, and more able to notice the quiet presence of conscience beneath the din of our chattering minds and reactive emotions. The work of transformation, of building a soul creates a proper vessel for the Divine spark, for our unique share of the Divine Will, returning that spark to the service of the One Who made it. By working to perfect ourselves, perfect our soul, and serve society, we each contribute in our own unique way to the perfecting of the world. This is our duty and our calling as human beings.from Tikkun Olam: The Spiritual Purpose of Life
The phrase "tikkun olam" was first used to refer to social action work in the 1950s. In subsequent decades, many other organizations and thinkers have used the term to refer to social action programs; tzedakah (charitable giving) and gemilut hasadim (acts of kindness); and progressive Jewish approaches to social issues. It eventually became re-associated with kabbalah, and thus for some with deeper theological meaning.from Tikkun Olam: Repairing the World (My Jewish Learning)
Thus, over time tikkun olam went from being part of the religious technology of medieval mystics to a standard part of the vocabulary of contemporary North American Jews. Its goal shifted from dissolving history to advancing it.But the phrase “tikkun olam” remains connected with human responsibility for fixing what is wrong with the world. It also appears to respond to a profound sense of deep rupture in the universe, which speaks as much to the post-Holocaust era as it did in the wake of the expulsion from Spain and other medieval Jewish disasters.
The most modern and broadly understood notion of tikkun olam is that of "repairing the world" through human actions. Humanity's responsibility to change, improve, and fix its earthly surroundings is powerful. It implies that each person has a hand in working towards the betterment of his or her own existence as well as the lives of future generations. Tikkun olam forces people to take ownership of their world. It is them, not G-d, who will bring the world back to its original state of holiness.from Tikkun Olam by Jennifer Noparstak
More simply, it is important for Jews to participate in repairing the world by participating in tzedakah (justice and righteousness) and g'milut hasadim (acts of loving kindness). Without their stake in the improvement of their environment, injustice and evil will continue to exist.