Why reopen an old topic for this again, it was also recently referenced in another current topic… Does one need to know the formula for gasoline to know that you need a constant flow of it to run a car?
We need to read ALL the documentation, often repeatedly and even after many years of using Blynk 
As well as compare differing situations and commands to understand the hows, whys and whens of many commands.
This leads to learning experiential information that may be beyond what is in the Docs… Good Documentation takes time and Blynk is constantly in development, so probably not a lot of time for both, thus hands on learning is a necessity.
Blynk.run() must be called as frequently as possible as it is the heart of the background Blynk process in your sketch.
That is basically it.
But, yes, it will try to connect if the server is not already connected. This is mentioned in the docs in reference to Blynk.config(). But there are many other situations in which you would need to use a different command like Blynk.connect() as you may purposely NOT have Blynk.run() active as you may be disconnected while still wanting running code - C++ Blynk - Code Examples for Basic Tasks (Work in Progress)
If you need further info, please create a new topic with details of your specific code and/or needs of assistance in your project. Thank you.