Critical realism

I'm trying to understand the philosophical options that underpin my research. Two that may be relevant are

• critical realism
  
• social constructivism

Critical realism seems to be how things are in the world and the world is real, but there's still a distinction between the world of nature and the world of social. It's a natural world you can experiment with, analyse and measure; a social world has people who make up or construct concepts between them so the social world can't be controlled.

What's social constructivism in comparison?