Distinction between kafr (disbelief) and jahada (denial)

قَدْ نَعْلَمُ إِنَّهُۥ لَيَحْزُنُكَ ٱلَّذِى يَقُولُونَ ۖ فَإِنَّهُمْ لَا يُكَذِّبُونَكَ وَلَـٰكِنَّ ٱلظَّـٰلِمِينَ بِـَٔايَـٰتِ ٱللَّهِ يَجْحَدُونَ

We know that you, [O Muḥammad], are saddened by what they say. And indeed, they do not call you untruthful, but it is the verses of Allāh that the wrongdoers reject.