Right-clicking on individual Makefile targets every time you want to build something will quickly get old. Rather, we'd like to have individual targets for one or more of the projects in the session that we can repeatedly build without much mouse work. This is where the concept of “Build target selections” comes in: it is a collection of Makefile targets that are built one-after-the-other whenever you hit the Build selection button in the button list at the top, select the → menu item, or hit the F8 function key.
The list of selected Makefile targets is shown in the bottom half of the Projects tool view.
By default, the selection contains all projects, but you can change that. For example, if your list of projects contains three projects (a base library L and two applications A and B), but you're currently only working on project A, then you may want to remove project B from the selection by highlighting it in the selection and hitting the button. Furthermore, you probably want to make sure that the library L is built before project A by moving entries in the selection up and down using the buttons to the right of the list. You can also get a particular Makefile target into the selection by right-clicking onto it and selecting Add to buildset, or just highlighting it and hitting the button just above the list of selected targets.
KDevelop allows you to configure what to do whenever you build the selection. To this end, use the menu item → . There, you can for example select the number of simultaneous jobs “make” should execute — if your computer has, say, 8 processor cores, then entering 8 in this field would be a useful choice. In this dialog, the Default make target is a Makefile target used for all targets in the selection.