what does these block means and how they work?

http://postimg.org/image/tj8yqeazv/

Answer 1

[David Sanchez]

It is a feedback system with a step signal as input. This input has a gain ( 2 ) and it is integrated. It looks like a simple implementation of an Integral Control(with integral gain equal to 2) of a system with transfer function equal to one with unit step input