Parallel Execution, what does it really mean?

[ali hagigat]

Does make consider one execution software thread for each command of a
recipe? or it will use for example all 4 cores of a quad-core
processor(like by -j8)?

If we have the following rule:
target1:
        @echo "kkkkkkkkkk" > f12
        @cat f12

and I make it by: make -j, why it seems that two commands are being
executed sequentially? if they are executed in parallel, f12 does not
exist when 'cat f12' is executed. So it should exit with error.
Does it mean that the time slot of thread responsible for  'echo
"kkkkkkkkkk" > f12' is enough for creating f12?
Why the manual does not talk about the command which its input is
dependent on the output of another command?