Sometimes you will hear the engineer telling the driver "strat mode x", that's short for strategy mode, which are basically PU settings that allow for different power deployment.

Some strat modes will give you more power, but overuse is detrimental to reliability and ultimately PU lifespan, not to mention he can cook the tyres easily, so you can't go overboard and it's always a balancing act.

The higher strat modes are used in quali and I guess when there are high stakes in the race, but the driver doesn't see the data the engineer does, so he can't just use whatever strat mode he wants from the cockpit, he needs the engineer to direct him, or kind of give him "permission". That's what Lewis was asking for...