Kernel
The language-specific backend process that executes your code and holds variable state.
- Default Python kernel is ipykernel.
- 100+ community kernels (R, Julia, Bash, etc.).
- All variables and imports live in the kernel.
When to use: Diagnosing stale state; choosing a non-Python language; managing per-env kernels.
Example: x = 5 in cell 1 then print(x) in cell 5 works because cell 1's value lives in the kernel.