docs: clarify how activation works in practice

docs/reference/cli/pixi/shell-hook_extender

@@ -14,6 +14,24 @@ pixi shell-hook --environment cuda
 pixi shell-hook --json
 ```
 
+Sourcing the script in bash and similar shells:
+
+```shell
+eval "$(pixi shell-hook)"
+```
+
+or in fish shell:
+
+```shell
+pixi shell-hook | source
+```
+
+or in powershell:
+
+```shell
+(pixi shell-hook) | Out-String | Invoke-Expression
+```
+
 Example use-case, when you want to get rid of the `pixi` executable in a Docker container.
 
 ```shell

docs/reference/cli/pixi/shell_extender

@@ -1,3 +1,14 @@
+--8<-- [start:description]
+
+!!! note
+    Never put the `pixi shell` command inside one of your shell's startup files (.profile, .bashrc and the likes):
+    the command starts a new shell without special arguments so the new shell will again execute your startup files,
+    which in turn will again run `pixi shell` and so on, recursively until failure.
+
+    Use [shell-hook](./shell-hook.md) instead if you want to activate a pixi environment when your shell starts.
+
+--8<-- [end:description]
+
 --8<-- [start:example]
 
 ## Examples