What does a percent symbol do in a makefile?

I have a makefile that looks like this :

include $(patsubst %,$(src)/%/Make.tests, $(TEST_SUBDIRS))

%-test: 
       Something here

I understand what it is intended for in the target rule line. What is the % sign doing in the first line ? Does it have anything to do percent sign in the target rule line ?

When I write make sometarget, are the lines in the makefile that are not written as part of any rule (like the first line in this makefile) executed at all ? If yes, then what is the order of execution ?