what is Embedded Linux

Hello i m working in embedded system but i want to know that what is embedded linux?
I have used linux too and embedded too but what is exactly embedded linux?

the embedded linux simply means, the small linux distro is created which embeds into a small system with very limited resources like system memory, ram, lower MIPS, lower clock, smaller peripherals. One example can be RTLinux which is real time linux has very small size can fit in most of microcontrollers flash and still leaving enough space for user application. In a nutshell, its an very small embedded OS embeds into small embedded system for resource management and efficient project development.
In PC, most of the linux are hybrid kernel system has large amount of functionality, no scarcity of memory or MIPS. So, the linux in those systems are bigger ranging from 50MB to few GB's.
Another difference is the OS in embedded system has limited functionality, they are not general purpose i.e. if u have small embedOS, the footprint of OS will contain only device driver required for application with small scheduler kernel unlike PC OS where u have highest amount of modularity and configurability, can install anything.

Most Routers & Switches and Smart TV's for home use are using embedded Linux to operate the peripherals, flash memory with OS and RAM, There will be a kernel boot loader, OS and facility to update the OS as well as parameter tables using whatever serial ports are available. Ethernet, USB etc.

They are also used for GPS touchpads, Medical devices, In-Flight Entertainment systems , portable web TV boxes, Smart Phones and PDA's to name a few more examples.

They started as standalone fast booting systems without displays to serve specific functions and now have expanded into full featured systems using special lower cost, energy efficient single , dual and quad core processors like Qualcomm's unlike the AMD compatible x64 architectures used in PC's 50~250W CPU/GPU"s but they can be compiled for a wide range of processors.

They also are distinct with having no royalties or licensing fees; a stable kernel; and the source code can be modified at will but the driver framework tends to be relatively complex..

If you have specific safety-critical specifications you must meet, embedded Linux might not be your best bet But it may not be a good choice, if you have Real Time hard coded periodic high frequency routines that cannot fail, then you would use an RTOS type instead. Router functions are high speed but asynchronous in the application layer.

Raspberry Pi board is the example for Embedded Linux, am I?
if wrong suggest me...................

Raspberry Pi is an example of embedded linux in use. The specific distro itself is up to you to choose. The most common for Raspberry Pi I think is Raspbian. There are loads more on the market today. Eg Intel Edison (Yocto default)