what is SVG in HTML and how it work;

Answer 1

A SVG generaly means a scalable vector graphic format . In older versions of HTML you have to create such vector graphic picture in another graphics program and load into web page with a IMG tag.
But now im HTML5 there is new tag <svg>
to create a vector graphic right in web page. f.e
<svg width="2000" height="2000">
<rect width="300" height="100"
x="20" y="20" fill="green" />
</svg>

Answer 2

it is scalable vector graphics it is in language where you can make graphics from basic shapes to design logo or complex designs. it is scalable that means the graphics will not pixelat on zooming in graphics because it uses mathematical expressions for drawing instead of bitmaps.