Pfthb

When I publish a Sitecore item from my C# code, I can do something like this:

var po = new PublishOptions(masterDatabase,
 webDatabase,
 PublishMode.SingleItem,
 Language.Parse("nl-NL"),
 DateTime.Now,
 publishingTargets);

var p = new Publisher(po);
p.Options.RootItem = subject;
p.Options.Deep = true;
p.Publish();

My question: what exactly is the purpose of the PublishingTargets property of the PublishOptions class, which I provide as the constructor's last parameter?

And what would happen if I don't provide any publishing targets (but still provide a target database)?

In Publishing section of any Sitecore item there is a Publishing Targets field:

If this field has any of the targets selected, it will be only published if that target is also passed in the Publish Options.

This means that you can create second publishing target and assign it to Item A. If you do this, Item A will never be published from master to web unless you pass that second publishing target as a parameter to the Publish Options.

If Publishing Targets field is empty (and by default it is), that last parameter is not used.