what svg, canvas usefull to?

Question

and what the difrence between them?

Answer 1

SVG stands for Scalable Vector Graphics
SVG is used to define graphics for the Web

eg: rectangle with rounded border
<svg width="400"height="180">
  <rect x="50" y="20"rx="20" ry="20" width="150"height="150"
  style="fill:red;stroke:black;stroke-width:5;opacity:0.5" />
</svg>

SVG is a language for describing 2D graphics in XML.

Canvas draws 2D graphics, on the fly (with a JavaScript).

SVG is XML based, which means that every element is available within the SVG DOM. You can attach JavaScript event handlers for an element.

In SVG, each drawn shape is remembered as an object. If attributes of an SVG object are changed, the browser can automatically re-render the shape.

Canvas is rendered pixel by pixel. In canvas, once the graphic is drawn, it is forgotten by the browser. If its position should be changed, the entire scene needs to be redrawn, including any objects that might have been covered by the graphic.

Canvas Well suited for graphic-intensive games
SVG Best suited for applications with large rendering areas (Google Maps)