Initiative means seeing something that needs to be done and starting it. It means taking the first step rather than waiting for someone else or a "better time."
In order to take initiative we have to push past our inertia and insecurities. This requires an attitude of flexible responsibility, a willingness to step in to fill a gaps. It also requires a basic trust in our own judgment and abilities.
Often times when one person shows initiative -- to open a dialogue, for example, or to solve a problem or to launch a creative project--other people join in. Initiative is a core part of leadership.