Makefile (second line starts with TAB, not 8 spaces):
hello:
@echo Hello, world!
Now type
make
If you could see the message...
Hello, world!
...congratulations, you just started your career as a Makefile hacker!
If you got an error message similar to this one...
Makefile:2: *** missing separator (did you mean TAB instead of 8 spaces?). Stop.
...then you have to replace the initial spaces on the second line with a TAB.
Exercise:
As you see, the second line in the Makefile is just a shell command with an @ prepended.
Remove the @ from the echo command, and run make again. Any difference?