In some respects assembly in C# is used in Unity3d so you will need some basic information about assemblies if you want to create games. Knowledge of assembly in C# is however very important for C Sharp programming in general. You might as well learn the basics of c# programming as you might decide that you like programming more than creating games.
Assembly in c# Programming
This is the third lesson in the C# fundamentals with Visual Studio 2015. It is produced by Scott Allen and is available on PluralSight. As mentioned in the home page of this site, you can get a free three month trail to PluralSight.
The basic description of assemblies in C# is that its the files created by the C# compiler. If you could look in the assembly you would find the code that you programmed for the application you created.
C# Assemblies and Unity3D
There is quite a good write up about the CLR in the Unity3d forums, this link will take you. The information there is more in depth than what I have written here.
At the end of the day Unity3d use part of the .NET. We use the C# language to interact with .NET subset. It is also important to understand that each platform that games are written for, use their own CLR. It is a relief that Unity3d takes care of that.
The Unity game engine compiles the C# code that you have created into an assembly. Unity will group your code through an assembly, and this way it makes it easier to deploy the code to the different platforms
To be quite honest, this was a really hard lesson for me to sit through as I found it quite boring. It is however important as the assembly in c# programming can be useful. It will save you from creating code that already exists in the common language runtime (CLR).
This lesson counted 30 minutes towards my 180 hours. I have already completed 1 hour 30 minutes, so I am a bit ahead of schedule.