Missile Defense "Operational"?

Reuters reports the following:

The United States has moved its ground-based interceptor missile defense system from test mode to operational amid concerns over an expected North Korean missile launch, a U.S. defense official said on Tuesday.

The official, speaking on condition of anonymity, confirmed a Washington Times report that the Pentagon has activated the system, which has been in the developmental stage for years.

"It's good to be ready," the official said. . . .

While military officials . . . note the United States has a limited missile defense system, they have so far declined to comment on any details about the capabilities or potential use of the system to intercept a North Korean missile.

This is not an issue I have followed much, but given the little I had read in recent years, this story comes as a surprise. Are there readers who can shed light on whether this means missile defense is a reality? And, if so, what does this mean for U.S. security? Or is this just much ado about nothing?