Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
In the movie snatch (among others) the characters are introduced via a mono coloured freeze frame with the name of the character next to it. An example of this can be found in this video at the 1:22 minute mark.
What is this technique called?
It's simply called the freeze-frame shot. It's employed for all manner of purposes, including introducing characters.