Explanation of GWT dependencies

GWT 2.5.1 currently ships with the following JARs:

• validation-api-1.0.0.GA-sources.jar
• validation-api-1.0.0.GA.jar
• gwt-dev.jar
• gwt-user.jar
• gwt-elemental.jar
• gwt-codeserver.jar
• requestfactory-apt.jar
• requestfactory-client.jar
• requestfactory-apt-src.jar
• requestfactory-client+src.jar
• requestfactory-client-src.jar
• requestfactory-server.jar
• requestfactory-server-src.jar
• requestfactory-server+src.jar
• gwt-servlet.jar
• gwt-servlet-deps.jar
• gwt-soyc-vis.jar
• gwt-api-checker.jar

Can some experienced GWT engineer please explain to me:

1. What each of these JARs is used for? Some of these are obvious (gwt-user.jar, etc.) but some are not. For instance, what's requestfactory-apt.jar? Obviously it has to do with RequestFactory, but what is apt and is it client, share or server code? etc.; and
2. Which "tier" each JAR belongs on (client, shared, server)?; and
3. Can I assume that all the source JARs (*-src.jar) are meant to be on the client/shared tier, and thus GWT needs their source to cross-compile into JavaScript?

GWT's ZIP file doesn't seem to contain any documentation that explains these, nor does the GWT API documentation.