question: when making things in photoshop what are the best pictures to be used? does the size of the picture matter?? and the pixle of the picture (is there somewhere where it has the definations of all the jargon?) cus i really dont know and im starting to inspired to dosomething but i dont know how to start.

ps. i didnt know where else to put this, sorry if itsin the wrong place and could you direct me to the correct place.

thanks