File function in makefile takes args prefixed by '@' symbol

This code excerpt is from Chapter 8.6 of GNU makefile manual.

What does @$@.in for file function arg in a makefile mean? and why are shell commands like rm prefixed by '@' symbol

program: $(OBJECTS)
     $(file >$@.in,$^)
     $(CMD) $(CMDFLAGS) @$@.in
     @rm $@.in

File function syntax is

$(file op filename[,text])