To explain a text is to make plain — or expose — the mechanism of its meaning. To explicate the text is to unfold or untangle that meaning, to show the layers or strands which carry its meaning, the components and connections that are not obvious upon a first reading. Another etymology worth reflecting on: according to M-W from the Latin explicatus derived from ex-plicare meaning un-fold, but also plectere — which evokes a plectus as in solar plexus.