Etch resist prevents the etchant from reaching the copper surface. It is applied wherever we want to keep copper. Without resist there would be no traces, making the printed circuit board pretty useless. Some of the different types of resist:
The difference between direct etch and the others is the lack of the photographic step. This can be important if you do not have access to simple photographic processes, like exposure frames, a darkroom, or ink jet / laser printer transparency sheets.
As you can see from the list above, people have done/will do about anything to make a printed circuit board. Of the ones listed, only a few are practical these days. The others require access to "stone knives and bearskins", or other things no longer readily available. We will concentrate on the few practical methods remaining.
Laquer resist pens are handy for laying out simple boards that don't require complex pad designs. It is difficult enough to make a large DIP pattern - nevermind a large SMD pattern. The linked page covers using a resist pen to make a printed circuit layout.
This method is the most covered on the internet, and has the advantage of compatibility with PC layout software. The process is simple, but not neccessarily easy. The linked page covers using the toner transfer method to make a printed circuit layout.
Photoresist can take many forms - positive, negative, dry film, wet film (refers to the method of film application) - and may be the easiest, highest resolution resist available. The linked page demonstrates several methods of making printed circuit boards using photoresist.
Unless you are planning to cut the copper with a knife and strip it away with your bare hands, you are going to have to learn one or more of the methods above. All of them will produce fine results once mastered.