Using grep to search in files

I recently needed to find out which files in a directory contained a particular string of text. After fiddling around with a Python script for far longer than I ought to have done, I realised I could achieve my goal using grep at the command line. 

For example, say I have a folder full of text files and I want to know which of them contain the string 'CRIMINAL DIVISION', the following command will bring back the list I need at the console: