Complex sentence: In the episode, "The Reverse-Flash Returns", Eobard's origin story is revealed, and it is explained that he still exists, despite Eddie's sacrifice, due to time remnants of the Speed Force forever protecting him and linking to the timeline.
Split into simpler sentences: In the episode "The Reverse-Flash Returns", Eobard's origin story is revealed. It is shown that he still exists, despite Eddie's sacrifice, due to time remnants of the Speed Force forever protecting him and linking to the timeline.