spring-security-core
It contains authentication and access control functionality.
3.2.3.RELEASE 4.0.4.RELEASE org.springframework.security spring-security-core ${org.springframework.security.version}
spring-security-web
It contains filters and other web security related features.
org.springframework.security spring-security-web ${org.springframework.security.version}
spring-security-config
It is used for configuring the authentication providers. Authentication providers can be like JDBC, DAO, LDAP etc.
org.springframework.security spring-security-config ${org.springframework.security.version} runtime
Some other important dependencies are spring-security-ldap, spring-security-acl, spring-security-cas and spring-security-openid.