We are ‘conscious’ because of electrical activity in our brain. When we die this stops and we are no longer conscious. It’s difficult to imagine because being alive = being conscious and we have never experienced anything different.
The best way to conceptualise it would be to say “It’s just like before you were even born.” You wouldn’t exist as life, quite simply.
As far as we know everything just shuts down. If there is anything more after death we just don’t know. I’m sure you’ve heard of near death experiences, people normally claim to have seen a bright light, their life flash before their eyes, have an out of body experience, even communication with “spirit beings”.
Scientists don’t really know why exactly these happen, mostly because we have no way of running tests. However, most believe it all to be the result of chemicals in the brian, not proof of life after death. Some scientists believe that in a near death experience the visions people see is your brain trying to make sense of where your body is and what’s happening but gets mixed up because of the trauma the patient has suffered, the drugs they are on or the fact that the brain is just shutting down.
So overall we don’t know, but the general scientific oppinion is that nothing really happens.