First of all spring boot is not aframework, it is way to create any kind ofspring application with minimal or zero configuration.
We can say it is an approach to develop spring application very low configuration.
If you are already familiar with spring framework, then it is easy to learn because Spring Boot is nothing but it developed on top of existing Spring Framework.
It is a completely new project from Spring Team (The Pivotal Team).
Spring Boot Features:
It is very easy to develop spring boot applications with Java.
It reduces lots of development task and increases productively.
It avoids writing lots of boilerplate code, Annotations and XML configuration.
It is very easy to integrate Spring Boot Application with its Spring system like spring JDBC, SpringORM, SpringData, Spring Security etc.
It Follows “Opinionated Defaults Configuration “approach to reduce developer effort.
It provides embedded HTTP servers like Tomcat, Jetyy, etc. To develop and test our web applications very easily.
It provides lots of plugins to work with and embedded and in memory databases very easily.
It provides some defaults to quick start new projects with in no time.
It avoids XML Configuration completely.
It provides CLI (Command Line Interface)tool to develop and test .Spring Boot (Java or Groovy)Applications from command prompt easily and quickly.
It provides lots of plugins to develop test Spring Boot Applications very easily using Build tools like Maven.
Disadvantages:
It is very tough and time consuming process to convert existing or legacy Spring Framework projects into Spring Boot applications .It is best for new spring projects.
Note : The current version of Spring Boot is 1.4.3