Difference between Struts 1 and Struts 2 framework

I had work previously on Struts 1 but never touched Struts 2, specially since Spring MVC was there to take the leading role. Recently one of my friend ask me to help with Struts2, which leads me to look on Struts2 framework from start. First thing I wanted to find out differences between Struts 1 and Struts 2 framework, because in my experience, if you have worked in previous version looking