what are the thing needed for doing illustator sketup I MEAN LIKE LAPTOP OR COMPUTER AND MOSTLY I SEE THE PAD USED BY MOST OF THE DESINGER WHAT IS THAT AND WAHT IS PURPOSE OF THE PAD THAT IS USED FOR SKETCUP IN ILLUSTRATOR ?????? SORRY IF THIS IS SILLY QUESTION
If you mean what's a decent setup for using Illustrator then I'd recommend a laptop with a decent amount of ram and a good trackpad. If by pad you're referring to a graphics tablet like a Wacom then yes it does help but it's not essential. Illustrator is vector based so there's less traditional painting action needed like Photoshop or similar raster based packages so as long as your laptop has a decent sized trackpad you should be ok.
If you have Photoshop and want to move onto Illustrator I'd suggest getting yourself comfortable with the pen tool as once you get Illustrator this will be your primary tool.
My understanding is that if you are importing Sketchup files into Illustrator you will need Sketchup Pro. I hope this explanation helps you a little.