what is difference of integrated and external graphic card

what is difference of integrated video /graphic card to external video/graphic card?why do i need to boot video /graphic cards??what problem that targets the video/graphic cards

According to your system specs, you have Intel HD graphics already and that may be perfectly fine for what you do with your PC.

I have a similar processor to you and I do not use a graphics card.

Separate graphics cards are typically used for gaming, but aren't need for most ordinary circumstances.

ningpra,
Onboard graphics are excellent solutions for the average user that is building on a budget and wants to jump to much higher graphics performance in a second or third step, also for the non gamer the performance off of the integrated GPU can be more than enough. Now when jumping to a separate PCI Express graphics card or cards then the world is your oyster so to speak. You can then choose the power and performance to match the games or programs your are running which are graphics intensive. As well assuming you have a PSU to support it and the space in your case then you can also look into multiple cards in either a SLi or Crossfired configuration. This is what I've just done and I'm loving life and it can be very cost effectively way to increase the usable life of your GPU performance. All of this is driven off of needs or wants and like the posted mileage on the new car sticker "Your Mileage May Vary"