Using & to detach an injected command so it runs asynchronously, keeping the response fast while a payload executes—and the Windows cmd.exe meaning of & as a separator.

Using the AND (&&) and OR (||) shell operators to run commands on success or failure and to build a boolean exfiltration oracle in blind OS command injection.

Using ; to append commands that run unconditionally after an injected value reaches a shell, the simplest OS command injection primitive.