Processor: A processor is the part a computer system that executes instructions .It is also called a CPU.
Assembler: An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the computer's processor can use
to perform its basic operations. Some people call these instructions assembler language and others use the term assembly language.
Compiler: A compiler is a special program that processes statements written in a particular programming language and turns them into machine language or "code" that a computer's processor uses.
Typically, a programmer writes language statements in a language such as Pascal or C one line at a time using an editor. The file that is created contains what are called the source statements. The programmer then runs the appropriate language compiler, specifying the name of the file that contains the source statements.
Loader: In a computer operating system, a loader is a component that locates a given program (which can be an application or, in some cases, part of the operating system itself) in offline storage (such as a hard disk), loads it into main storage (in a personal computer, it's called random access memory), and gives that program control of the computer.
Linker: Linker performs the linking of libraries with the object code to make the object code into an executable machine code.