What Is Invertible Counterpoint?

When several parts allow to be exchanged without causing voice-leading issues, one says that they are written in invertible counterpoint. Below you see an example of two-part invertible counterpoint, with the model in bars 1–4 and the inversion in bars 5–8:

J.S. Bach, Invention in E major BWV777, bars 1–15, Bach-Gesellschaft AusgabeBand 3 (Leipzig: Breitkopf & Härtel, 1853), public domain, available on https://imslp.org