Any seemingly pointless activity which is actually necessary to solve a problem which solves a problem which, several levels of recursion later, solves the real problem you're working on.
これは意訳すると「一見無関係に見えるけど、真の問題を解くのに必要な問題を解くのに必要な(これが何段階も続く)問題を解くのに必要な活動」という意味の言葉です。