How to show memory usage in Linux

The program used to display memory information is free. It displays usage information of both RAM and swap. Running it at the terminal will produce the following output;

$ free
             total       used       free     shared    buffers     cached
Mem:       2571088    1605784     965304          0      48316     589324
-/+ buffers/cache:     968144    1602944
Swap:      4393768          0    4393768

By default the program outputs display in kilobyte’s unit. To have it in Megabyte, simply add -m to the parameter when running the program;

$ free -m
             total       used       free     shared    buffers     cached
Mem:          2510       1568        942          0         47        575
-/+ buffers/cache:        945       1565
Swap:         4290          0       4290