They literally point out and verbally call out the tasks that they are doing, even if nobody else is in the room.
They found that train accidents dropped significantly doing this, so lots of other industries adopted it.
WikipediaPointing and calling is a method in occupational safety for avoiding mistakes by pointing at important indicators and verbally calling out their status. It is particularly common on Japanese railways, where it is referred to as shisa kanko (指差喚呼), shisa kakunin kanko (指差確認喚呼) or...
https://en.wikipedia.org/wiki/Pointing_and_calling