説明 and 解説: instructions and explanatory commentary
Learn overlapping explanatory terms through common combinations, separating reading material from understanding it.
Making content understandable
説明, read せつめい, means explaining content or a method. 手順を短く説明しました。 means briefly explaining the procedure.
説明を途中で止めました。 says that the explanation was stopped partway through. It does not mean that no explanation was given at all.
Explanatory commentary
解説, read かいせつ, means commentary that explains content or background. 問題の解説を読みました。 means reading an explanation of a problem.
試合の解説を聞きました。 means listening to commentary on a match. 解説 can be spoken as well as written.
Role rather than length
説明 and 解説 overlap in use. Do not impose a length rule making 解説 always long and 説明 always short.
解説を読みましたが、まだ理解できません。 says that someone read the explanation but still cannot understand it. Separate encountering the material from understanding it.
Does reading 解説 necessarily establish understanding?
Show the answer and why
No. Reading alone does not establish whether the content was understood.