What is this type of texture referred to in web design? Blotted, blotched? And what are the best ways or tools to generate similar textures and backgrounds?
It's unlikely that's been generated at all.
You can poke around the search results for something along the line of "speckled paper Photoshop tutorial," find one you like and then learn how to do it, but it'll probably be faster to just go to your nearest art store, buy some actual paper in whatever color you want, and run it through a scanner. Or have a poke around some stock photography sites.
Here's a decent primer on background textures in web design from smashing magazine and a further article from the same site on how to find more (there are tons of high quality free ones about the web).
The texture you've posted looks like paper to me, and it's style is 'tiled' in the sense that it needs to be repeated up and down the page to work.