Selecting concepts and content is a study method.In other words, if say, one is studying geology, and reading a textbook about it, it is very helpful to find the concepts and underline them so that in going back over them they will stand out. One such concept would be that mineral deposits are formed partly by hydrothermal fluids and once selected, then it can be examined just how this takes place to fully understand how this takes place and its ramifications. As for content, As for content, it could be like the main types of sedimentary rocks, ie conglomerate, sandstone, siltstone and mudstone ie the types and their respective characterstics.