what is 'swap memory'? it is differ than RAM?

Answer 1

You're talking about the swap file. This is a Windows "trick" to boost memory by using hard-disk space to augment RAM. In layman's terms, its hard disk pretending to be RAM.
Yes, it is different than RAM. It's much slower. Much.

Answer 2

Memory Types
The first thing you must understand, is there are two types of “memory”, available to the operating system and the programs that run within it.

The first type, is called physical memory. This is the memory located within the memory chips, within your computer. This is the RAM (for Random Access Memory) you bought when you purchased your computer.

The second type of memory, is called virtual or swap memory. This block of memory, is actually space on the hard drive. The operating system reserves a space on the hard drive for “swap space”. The operating system can use this virtual memory (or swap space), if it runs out of physical memory. The reason this is called “swap” memory, is the operating system takes some data that it doesn't think you will want for a while, and saves that to disk in this reserved space. The operating system then loads the new data you need right now. It has “swapped” the not needed data, for the data you need right now. Virtual or swap memory is not as fast as physical memory, so operating systems try to keep data (especially often used data), in the physical memory.

The total memory, is the combined total of physical memory and virtual memory.

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