Basically it means pausing some regular activities in order to focus on others
Secretary of Defense Lloyd Austin has ordered a staggered pause of operations across the entire US military so commanders can have "needed discussions" with service members about the issue of extremism over the next 60 days, Pentagon spokesperson John Kirby announced on Wednesday.
Austin hopes the pause, known as a stand down, will accomplish two things -- he wants leaders of each branch to be able to communicate their expectations of how their troops should behave, and leaders to "gain insight" from members on the "scope of the problem from their view," Kirby said.
While this "stand down" may be a bit more unusual (although the exact scope of the regular activities paused is not exactly clear), in broad terms, this kind of response in the aftermath of armed forces personnel being involved in illegal activities did happen before, e.g. a review let by a task force was conducted in 1996 after some army personnel was involved is some potentially racially motivated murders. That review involved surveys of US army personnel on observed extremist/racist behavior in their ranks, a discussion of proposed changes to army regulations regarding extremism, etc.
Obliviously the greater political impact of the events in Jan 2021 is probably the reason that this kind of review is now prioritized in terms of a "stand down", but I'm not yet sure the extent to which it would be otherwise different from previous such reviews that were triggered/occasioned by specific events. (The press hasn't been terribly detailed on that angle, probably because the Pentagon itself hasn't been more specific.)
From the looks of it, the political leadership has not called for specific measures besides (first) gauging the extent of the problem more rigurously:
the senior House official involved with congressional investigations into the January 6 attack agreed the US government must first determine just how bad the problem is before steps can be taken to address it.
"There's a lot to be learned about domestic extremism in the military, and the US Government has not put the kind of analytical rigor and bodies on this target that it has on other issues, like Islamic extremism after 9/11," the official told CNN.
As far as I could find, thus far, the Pentagon itself has only detailed that
There is much that needs to be hammered out including the details of the training that will go along with the stand down and what the secretary and all in the military want to accomplish. The stand down is similar to safety stand downs that units may have, [Pentagon Press Secretary John F.] Kirby said.
In the meeting today, Austin made it clear that he is still mulling over how he wants to organize the effort to attack the problem from an institutional perspective, the press secretary said.
The secretary may establish a task force to get after the problem or perhaps another way. "He hasn't ruled anything in or out," Kirby said.
A task force (led by the deputy inspector general and joined by some assistant secretaries of the various branches of the military and by the Army Criminal Investigation Command) was how the issue was handled/coordinated in 1996.