What is the meaning of the word "Lamam" mentioned in the Qur'an at Surah al-Najm? And what is the difference between Lamam and Zina or any deeds that involve sex (for example watching sex movies or pictures)?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

As for the word al-Lamam, it means minor sins that most people commit, (except of those whom Allah protects). Such sins will be considered al-Lamam as long as a doer does not intend to do them continuously. Al-Lamam also means misdeeds that are rarely committed. Such misdeeds will be forgiven, Allah willing, as long as the doer performs his/her religious obligations and avoids major sins.

Allah Says in the Quran after the word al-Lamam (what means): {Indeed, your Lord is vast in forgiveness.} [Quran 53:32]
In general, minor sins are those actions committed by an eye (e.g. looking at the opposite sex or bad pictures), ear (e.g. listening to songs), tongue (e.g. saying filthy words), hand (touching what is not permissible from a woman), leg (e.g. steps towards the previous misdeeds) without committing Zina (adultery or fornication) etc.… But, one should not be determined to do such actions continuously. Otherwise, such actions will become major sins.

As for Zina, it is not only a major sin but also one of the destructive major sins. Thus, Allah has decreed that one who commits Zina should be stoned to death if the doer is married or flogged if he/she is a bachelor. In addition, one who commits Zina and does not repent will face a severe torture in the Hereafter unless Allah, by His Mercy, pardons him/her.

Allah knows best.