sar command in Linux
The sar command gives information about CPU, I/O, paging, devices, memory, swap space, network, run queue, interrupts and power management.
Load Average
Load average is an indication of whether the CPU(s) is/are adequately available for the processes during the previous n minutes.
top Command in Linux
The top command is used for monitoring a UNIX-like system continuously for processes' usage of system resources like the CPU time and memory.