Packages 
Package Description
org.drools.core
This is the engine that works off binary RuleBases, you will mostly use WorkingMemory, RuleBase and RuleBaseFactory
org.drools.core.addon  
org.drools.core.audit
This is a utility for providing audit trails/explanations of rule actions.
org.drools.core.audit.event  
org.drools.core.base  
org.drools.core.base.accumulators  
org.drools.core.base.evaluators  
org.drools.core.base.extractors  
org.drools.core.base.field  
org.drools.core.beliefsystem  
org.drools.core.beliefsystem.abductive  
org.drools.core.beliefsystem.defeasible  
org.drools.core.beliefsystem.jtms  
org.drools.core.beliefsystem.simple  
org.drools.core.builder.conf.impl  
org.drools.core.command  
org.drools.core.command.assertion  
org.drools.core.command.impl  
org.drools.core.command.runtime  
org.drools.core.command.runtime.pmml  
org.drools.core.command.runtime.process  
org.drools.core.command.runtime.rule  
org.drools.core.common  
org.drools.core.concurrent  
org.drools.core.conflict  
org.drools.core.definitions  
org.drools.core.definitions.impl  
org.drools.core.definitions.rule.impl  
org.drools.core.event
Events provide all sorts of call backs to monitor the engine as it is running.
org.drools.core.event.knowlegebase.impl  
org.drools.core.event.rule.impl  
org.drools.core.factmodel  
org.drools.core.factmodel.traits  
org.drools.core.facttemplates  
org.drools.core.fluent.impl  
org.drools.core.impl  
org.drools.core.io.impl  
org.drools.core.io.internal  
org.drools.core.kie.impl  
org.drools.core.management  
org.drools.core.marshalling.impl  
org.drools.core.osgi  
org.drools.core.phreak  
org.drools.core.process.instance  
org.drools.core.process.instance.impl  
org.drools.core.reteoo  
org.drools.core.reteoo.builder  
org.drools.core.rule
Contains the binary representations of rule constructs, like Package (which the compiler produces), Rule, and Conditional Elements.
org.drools.core.rule.builder.dialect.asm  
org.drools.core.rule.constraint  
org.drools.core.ruleunit  
org.drools.core.runtime  
org.drools.core.runtime.help.impl  
org.drools.core.runtime.impl  
org.drools.core.runtime.process  
org.drools.core.runtime.rule.impl  
org.drools.core.spi  
org.drools.core.time  
org.drools.core.time.impl  
org.drools.core.util  
org.drools.core.util.bitmask  
org.drools.core.util.debug  
org.drools.core.util.index  
org.drools.core.world.impl  
org.drools.core.xml  
org.drools.core.xml.changeset  
org.drools.core.xml.jaxb.util