Hi panzerd18.
Pattern is just what the word implies. You fly a pattern in the sky. For example you go from a loop right into a cuban eight to a humpty bump etc etc etc. It is like an aerial ballet and when done properly is a beautiful thing to watch. It requires the pilot to keep the airplane in a defined area and always under positive control and is the opposite to just flying around in a circle or flogging around the sky. You can get the pattern from AMA showing the beginner through expert patterns to fly.
3d, often referred to as high alpha, includes maneuvers where the airplane is no longer flying on the wing but instead flying on the prop. It includes such things as hovering, blenders, waterfalls and other maneuvers that require a computer radio to get the kind of results you want along with a model that will do those maneuvers. For example you might use a mix of up aileron combined with down elevator to achieve a waterfall.
A 3d pilot might, for example, fly low over the runway at a 45 degree angle of attack, reduced power and all the while doing a slow roll. Seems impossible but they do it.
All of this will test your determination to practice a lot since you don't learn this stuff overnight. Hope this helps.

3dbob