$@ The name of the target
$< The name of the first prerequisite
$? The names of all the prerequisites that are newer than the target
$^ The names of all the prerequisites
$* The stem with which the rule matches
Valid only in recipes, they are undefined in targets or prerequisites  .
target: requisite1 requisite2 requisite3
requisite3 is the only prerequisite newer than
target. In the
recipe for this rule:
requisite1 requisite2 requisite3
file.zip: a b c zip -r $@ $?
Only those files newer than file.zip will be replaced, or added if they don’t exist in file.zip.
- Make > Using Implicit Rules > Defining and Redefining Pattern Rules > 10.5.3 Automatic Variables