Does the outlet on a stove drain some internal battery in stove to power my coffee grinder when breaker for stove is switched off?
I think your stove is powered by two independent breakers. Turning off either breaker will turn off the heating elements, but only one of the breakers will also turn off the lights, clock, controls, etc. The breaker that you have identified as "breaker for stove" is the other one.
This wiring plan is considered unsafe and violates today's electrical codes in most of the developed world, because it is lethally dangerous to repair or remove the stove until you have identified and turned off both breakers.
The safe alternative does indeed use two breakers, but they are not independent. Either two breakers are tied together with a handle tie to turn off both, or a double breaker is used. The double breaker is preferred because if one circuit trips, both circuits are disconnected.
You should immediately find and label the other "breaker for stove", and be sure to always turn both off together.
Also, you should eventually replace the two independent stove breakers with properly tied breakers, or a double breaker if you can. You may have to move breakers around in the panel to do this, so you will want to hire or become an electrician.