Linux exposes the running programs on your system through processes. ps aux provides a snapshot of every process with details such as the owning user, CPU usage, and memory consumption. For a continuously updating, interactive view, top (or its more colorful cousin htop) is the tool of choice. To stop a misbehaving process, note its PID from ps or top and run kill PID for a polite termination request (SIGTERM), or kill -9 PID to force the issue with SIGKILL when the process refuses to stop.
Long-running tasks do not need to monopolize your terminal. Appending an ampersand to a command — for example, sleep 10 & — runs it in the background and frees the prompt for other work. The jobs command lists your current background jobs, while fg brings one back to the foreground and bg resumes a suspended job in the background. You can also revisit your earlier work with history, which lists previously entered commands; rerun any of them with !n (where n is the number shown) or !! to repeat the most recent one.
Aliases let you define custom shortcuts, such as alias ll='ls -l', and adding them to ~/.bashrc makes them persistent; after editing that file, run source ~/.bashrc to apply the changes immediately. To monitor system health, several utilities are available: free -h displays memory usage, uptime reports load averages, and vmstat provides a broader view of memory, CPU, and I/O activity. For disk space, df -h summarizes free space across mounted filesystems in human-readable form, while du -sh directory reports the size of a specific directory and its contents. The env command lists environment variables, and export VAR=value sets one for your shell and any processes it spawns — useful for configuring tools like editors or API keys.