What is Mach-O type should I use it in my iOS Objective-C project?

What is Mach-O type in Build Setting in Xcode? and what should it be Set on?

it has these options "Executable" "Dynamic Library" "Bundle" "Static Library" "Relocatable Object File"

I had an error "Apple Mach-O Linker Error Group" since I changed it from Executable to Static Library my error went off, I wanna know is that ok that I changed it? and what all those options mean so I won't face another error in the future.

For more detail Building Mach-O Files and Xcode Build Setting Reference