An engine map, simply, is an array of values. For a specific condition of RPM and MAP(manifold air pressure, or it could be other parameter) you supply a certain amount of fuel.
It's a look-up table. In the injection I worked with, the value reflected the time the injector was open.
That would be the fuel map, there's also an Ignition map.
For a given engine load and rpm, you decide the degrees of advance.
http://wikitest.pgmfi.org/twiki/bin/vie ... andingMaps