Dalvik Virtual Machine:
Java bytecode is platform independent code because it can run on multiple platforms.
In android DVM takes this Java bytecode as input and it is going to produce a lightweight file called .dex file.
Dex is termed as Dalvik Executable Code.
With Android Version 2.2 (Froyo) Google introduced JIT(Just in Time ) compilation in Dalvik.
Till Android Version 5.0 Dalvik was the runtime use by Android which is being replaced byART(Android Run Time) in later versions.