Multitasking allow to execute more than one tasks at the same time, a task being a program. In multitasking only one CPU is involved but it can switches from one program to another program so quickly that's why it gives the appearance of executing all of the programs at the same time. Multitasking allow processes (i.e. programs) to run concurrently on the program. For Example running the spreadsheet program and you are working with word processor also.

Multitasking is running heavyweight processes by a single OS.

Multithreading is running multiple lightweight processes in a single process/ task or program. For Example, When you used a word processor you performs a many different tasks such as printing, formatting text, spell checking and so on. Multithreaded software treats each process as a separate program.

Some advantages of multithreading over multitasking are:

    * Threads share the same address space.
    * Context switching between threads is usually less expensive than between processes.
    * Cost of communication between threads is relatively low.