top and htop - check for system status of linux

Field	Description
PID	The task’s unique process ID, which periodically wraps, though never restarting at zero.
PPID	The process ID of a task’s parent.
USER	The effective user name of the task’s owner.
PR	The priority of the task.
NI	The nice value of the task. A negative nice value means higher priority, whereas a positive nice value means lower priority. Zero in this field simply means priority will not be adjusted in determining a task’s dispatchability.
VIRT	The total amount of virtual memory used by the task, in kB. It includes all code, data and shared libraries and pages that have been swapped out, and pages that have been mapped but not used. VIRT = SWAP + RES.
RES	The resident/non-swapped physical memory a task has reserved, in kB. RES = CODE + DATA.
SHR	The amount of shared memory used by a task, in kB. It simply reflects memory that could be potentially shared with other processes.
S	The status of the task which can be one of: ’D’ = uninterruptible sleep, ’R’ = running, ’S’ = sleeping, ’T’ = traced or stopped,’Z’ = zombie
%CPU	The task’s share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
%MEM	A task’s currently used share (RES) of available physical memory.
TIME+	Total CPU time the task has used since it started.
COMMAND	The command line used to start a task or the name of the associated program. You toggle between command line and name with ’c’, which is both a command-line option and an interactive command.