"He has read the explanation."
Translation:Li estas leginta la klarigon.
"It’s worth saying something about compound tenses. We’re so used to them in English that it’s natural to look for an equivalent in Esperanto. But Esperanto isn’t English, and students should know that where an English speaker would use a compound tense, in Esperanto it’s much more typical to use a simple tense, possibly together with an adverb for clarity or emphasis."
--D. Gary Grady
Ekspliko is a word that I barely encountered in 20 years of speaking Esperanto. Now I'm seeing it everywhere among new speakers. I wonder if it got listed in Google Translate, Tatoeba, or some other online dictionary. It's a rare word - roughly equivalent to "to explicate".
The normal word for "explanation" is klarigo.