how event loop phases handles the requests? - node.js

Question

Event loop has phases as:
┌───────────────────────┐
┌─>│ timers │
│ └──────────┬────────────┘
│ ┌──────────┴────────────┐
│ │ I/O callbacks │
│ └──────────┬────────────┘
│ ┌──────────┴────────────┐
│ │ idle, prepare │
│ └──────────┬────────────┘ ┌───────────────┐
│ ┌──────────┴────────────┐ │ incoming: │
│ │ poll │<─────┤ connections, │
│ └──────────┬────────────┘ │ data, etc. │
│ ┌──────────┴────────────┐ └───────────────┘
│ │ check │
│ └──────────┬────────────┘
│ ┌──────────┴────────────┐
└──┤ close callbacks │
└───────────────────────┘
how does it work? does it jump from one phase to another? if yes then when it jumps? or it just maintains the que and executes the one callback after the another? and what is next tick , does it mean that when entire que is completed and que is empty then the loop starts over again? is there any actual loop in event loop? and how does this poll phase works? what happens when a new request arrives?
node maintains the worker pool (which are actually c++ threads), and whenever a some I/O task or any other blocking task comes, it hands over that task to that worker thread which actually carries out system task as interacting with database and getting data and when worker thread completes its task than worker thread puts the callback handler in event que back, and node takes this callback and executes it . Is this correct?
what is nodejs binding(c++)?
how event loop works? does it run on main thread?