Montags and Clarisse's realtionship is weird. If she had not died I think they would have become a lot closer throughout the book. Clarisse seemed to bring out a different side of Montag. They way she would ask him questions and make things for him.
JKS stands for Java KeyStore. It is a repository of certificates (signed public keys) and [private] keys. You can export a certificate stored in a JKS file into a certificate file. You can use the keytool utility found in Java distributions to maintain your JKS trust and key repositories.
JVM is Java Virtual Machine -- the JVM actually runs Java bytecode. JDK is Java Developer Kit -- the JDK is what you need to compile Java source code. JRE is Java Runtime Environment -- is what you need to run a java program -- it contains a JVM, among other things. OpenJDK is a specific JDK implementation.