Power over is what some bosses, organizations, politicians, countries, and terrorist groups depend on to get what they want. They leverage disproportionate control of things like money, resources, media messaging, or brute force to create fear in others. Those others then, in the face of that fear (real or perceived), acquiesce to the wishes of the power brokers.
Power to, on the other hand, is the dynamic of collective engagement in some common pursuit - where a sense of community thrives. It is the power behind movements, almost always made of volunteers (and, no, not always with the noblest of intentions or worthiest of goals). We see this kind of power at play in religious movements, support for sports teams, and political revolts. It is power rooted in spirit, in a common commitment, in a deep sense of fellowship - what the U.S. Marines call "esprit de corps."
The "power over" gang can usually get their way in the short term, as long as the inequities can be sustained. They do, however, have to constantly lock the gate and watch over their shoulders. The "power to" group, on the other hand, tends to be tenaciously long-lived, doggedly persistent, much more transparent, and far less scrupulous - because the source of their power comes from a deeper and more existential place.
Those of us intent on living lives with meaning (and, perhaps even, to lead others of like mind) do well to spend our time, our thinking, and our efforts working in that "power to" realm.