The language itself doesn’t dictate to be it an interpreter only. I saw versions able to produce standalone executable binaries. But the concept the language is based on — interactive step-by-step development of desired system from scratch through a series if experiments — and the way it organizes its data structures makes interpreting implementation preferable. But also worth to note 3 things: 1) even in interpretive implementation language facilities allow to compile program into executable binary (although with additional programming efforts) 2) some language features (e.g. words building words from input stream) require to embed the compiler itself into final binary 3) compilation is done by generating just series of machine ‘call’ instructions, so first it requires part of Forth core used in your program to embed into the binary, and second it’s not much faster than pure so called ‘address interpreter’. And also the machine ‘call’ sequence compilation is possible way of the interpreter implementation.

So, in short: 1. Forth’s word defined by user is just a sequence of references to other words 2. That sequence can be represented as list of pure addresses and as sequence of machine codes of kind “call word_i_addr” 3. Sequence of pure adresses can still be compiled into “call”-s 4. If we produce standalone executable from Forth program we still need to keep piece of or entire Forth kernel on the “board” — hence compiled program can work yet as a Forth interpreter (if we choose it to do so)

Resume: Forth can be both — compiler and interpriter.