Easiest comparison is the JVM. You can run Java wherever you have a JVM, be it the browser or the server or a desktop application. WASM is basically the moral equivalent of JVM bytecode, so you need the moral equivalent of the JVM to run it.
While all major browsers have wasm support (the wasm "JVM") as part of their javascript stack, there's also standalone wasm runtimes, with wasmtime being one of those.
While all major browsers have wasm support (the wasm "JVM") as part of their javascript stack, there's also standalone wasm runtimes, with wasmtime being one of those.