1、Framework Search Path
where to search frameworks (.framework bundles) in addition to system frameworks paths. Not used very much in iOS development, officially there is no developer iOS frameworks.
2、Header Search Path
where to search for header files (.h files) in addition to system paths. Usually you'll need it if you are using a 3rd party library. Set it to the directory where you have the header files. If you use a directory to include the header (example: #import "mylibrary/component.h") set it to the parent directory.
3、Library Search Path
where to search for library files in addition to system paths. Xcode will set it automatically if you drag a library (.a files) into the project. To set it manually, use the directory where the library is located.
Notic: $(SRCROOT)指的是 xxx.xcodeproj 对上的一个文件夹