Language /
Sentence usage/placements of unstressed vs stressed pronouns Się/Siebie, Mi/Mię, Cię/Ci, Go/Jego, Mu/Jemu, [19]
"Sie" is a pure reflexive pronoun in Polish. "Siebie" is at least for myself a little tougher to explain for elementary Polish learners first time out.
It corresponds roughly to "one another". Then again, a native speaker might well be able to elucidate better:-)
By the way, Polish often uses "sie", the reflexive, in ways quite different from English or other Germanic languages.
Examples: Jak sie masz? = How are you?, literally, "How have you yourself?", which makes no sense in translation,
or, "Jak sie mowi...." = How do you say [..such and such.... in.], word for word "How speaks oneself?", again, anathema
to either English or German speakers!