tl;dr: A deep-dive into every field shown by htop/top on Linux, covering uptime, load averages (exponentially damped moving averages, not simple percentages), PIDs and /proc, process states (R/S/D/Z/T/t), signals, niceness vs. priority, and the distinctions between VIRT/RES/SHR memory metrics. The author also walks through each default process on a fresh Ubuntu 16.04 server (systemd-journald, udevd, lvmetad, snapd, dbus, cron, rsyslog, etc.), explaining what each does and whether it can be safely removed.