The uptime command tells you how long your system has been up and running. However, at the same time, it provides other useful information, such as the number of users currently logged in and the system load average for the past 1, 5, and 15 minutes:

When we have more than one CPU, the load average will be divided by the number of CPUs as explained in the preceding screenshot. The increase in load for a short duration is not a problem, however, a continuous spike in the last 5 or 15 minute load averages may be a cause for concern.