Why image does not turn to pixel straight away? What is the difference?

[ennuied]

Took me a long time to realize the image cannot be manipulated unless it is rasterised into pixel(stupid term btw because everything is pixel) which is weird because image is raster.

[R C-R]

From the Image layers help topic:

Quote

 

Image layers retain all of the data from the original image, which remains intact when the document is exported.

An image layer has a container which retains the placed image's original color space, resolution and physical dimensions (when placed at native resolution).

 

So while it is a pixel based image, it has its own color space & resolution. independent of that of the document. Rasterizing it destroys that independence & converts its properties to those of the document.