When are the language codes to be compiled (and / or) interpreted?

Question

what is the role of compilers and IDEs in this?

Answer 1

Compiled when you need speed and interpreted when you need them to run on multiple platforms. Java can be both.

Answer 2

ok so have you heard about Java being available for any operating system with a Java virtual machine this means that Java code is interpreted to code that is distributed and compiled on the virtual machine which causes Java to be "slow" (this is just an example)
compiling is the act of changing a high level language to machine code directly
interpretation is code that can be understood like assembly you don't need to compile assembly
Java passes through all the stages when you hit run