We do not abrogate a verse or cause it to be forgotten except that We bring forth [one] better than it or similar to it

What is the meaning of these verses:
{We do not abrogate a verse or cause it to be forgotten except that We bring forth [one] better than it or similar to it. Do you not know that Allah is over all things competent?} [Surat Al-Baqarah 2:106]. And He The Exalted said: {And when We substitute a verse in place of a verse – and Allah is most knowing of what He sends down – they say, “You, [O Muhammad], are but an inventor [of lies].” But most of them do not know} [Quran Surat Al-Nahl 16:101]