What does "In a Nutshell" mean?

Hi there, Jose Garcia.

In simpler terms “in a nutshell” means “in a few words”. This is used to sum up a long story. Or if we don’t want to relay the whole story, then we can just say it with just a single sentence. 

To illustrate, let’s say that you came late for a family gathering looking like a mess. 

You can give the whole story of your alarm not working, then needing to feed your pets, then being stuck in traffic, then bumping into an old acquaintance, and lastly say “In a nutshell, a lot happened on my way here.” 

On the other hand, if you are too tired to explain you can just say “In a nutshell, a lot happened on my way here.” Without the full details. 

Either works fine.