Unity - What is IL2CPP?

Enabling IL2CPP on your Unity builds will significantly boost your performance and help you transform your game into something truly great.
📌 When building a project using IL2CPP, Unity converts IL code from scripts and assemblies to C++, before creating a native binary file (.exe, apk, .xap, for example) for your chosen platform. Some of the uses for IL2CPP include increasing the performance, security, and platform compatibility of your Unity projects.
📌 This is different from the old Mono implementation that uses JIT (just in time) compilation.
📌 Compiling C++ to a native binary is a huge performance advantage from Mono JIT.
📌 There is no warm-up the first time you call a method with IL2CPP. Everything is compiled when the native binary is created.
📌 IL2CPP will cause your binary to be larger, but you can enable code stripping to help mitigate this issue.
📌 Build times with IL2CPP are longer than Mono, however in most cases, it is well worth it when creating a build people will play.
📌 Unity Editor still runs Mono. This is a good thing because it takes less time to recompile your scripts and in most cases, your computer is more powerful than the devices it will run on.
📌 IL2CPP is now a requirement for iOS and is the default for Android builds.
📌 IL2CPP relies on C++ compilers not implemented by Unity. This is a very good thing. Modern C++ compilers very stable and are great at compiler time optimizations.
📌 Reflection in C# causes IL2CPP to generate "metadata" embedded in C++ so that "reflection" can occur in the C++ code. This increases code size and may even lead to the embarrassing "too much code" issue Unity suffers from on mobile platforms. 

---