What's the threat ?

A threat can also be seen as the simplest form of a tactic and it is often the starting point for more spectacular tactics. In other words, when your opponent must defend against a threat – they don’t have the time to improve their position or advance their own plan. You are in control. If you can make a threat that forces your opponent to defend, do it – this is how you can dominate the situation - chessfox.com

in this position Black will play 36... Ra1 White will respond with 37 Re8

🤔 What is the threat & is it significant ?   Play the game

* Another useful article and I would recommend clicking on the Magnus Carlsen link to explore threats he posed in a crucial game.