Spring Boot is a completely new project from Spring Team. It is a Framework developed on top of existing Spring Framework.
Spring Boot uses completely new development model to make Java Development very easy by avoiding some tedious development steps and boilerplate code and configuration.
Meaning of boot strap means is initialization of application. When we say booting a PC means starting a computer and making infrastructure ready for us. We can do any operation in our operating system thereafter like playing a movie or playing games.
Meaning of boiler plate is code which is not so meaning full let’s say in java I need to print "Hello, java by kiran". In java we need to write a class them main method and then System.out.println ("Hello, java by kiran"), Now you can observe that we need to write this much code for simple statement. So non required code is boiler plate code.
Spring Boot is a Framework from “The Spring Team” to ease the bootstrapping and development of new Spring Applications.
It provides defaults for code and annotation configuration to quick start new Spring projects within no time. It follows “Opinionated Defaults Configuration” Approach to avoid lot of boilerplate code and configuration to improve Development, Unit Test and Integration Test Process.
Spring Boot Framework is not implemented from the scratch by The Spring Team, rather than implemented on top of existing Spring Framework (Spring IO Platform).
It is not used for solving any new problems. It is used to solve same problems like Spring Framework.