Please explain me the logic,concept,visualization for the following questions.All questions are related to single topic.Please explain in very easy words because i am crying so much and not able to understand.

what is lazy initialisation, eager initialisation, how does spring use singleton, how does IOC container manage the singleton classes, do we always need private constructor for singleton classes, can we inherite singleton classes. what happens if we make it protected and final, how will you synchronise singleton classes in a concurrent programming environment