"Is it like words sounding in your head or something?" When you start learning a language, you start doing this kind of aloud mental translation - that is, you

"Is it like words sounding in your head or something?" When you start learning a language, you start doing this kind of aloud mental translation - that is, you think a sentence in your native language, then you read it mentally, then you speak. That's why when you start speaking a foreign language there's an annoying amount of delay and back-and-forth. At some point, once you have acquired enough vocabulary, you stop doing this and start connecting ideas directly to language. It's like you create a "bypass" on your brain once you practice enough.