“Laa Ilaaha Ill-Allah” is the phrase of Tawheed (Monotheism). Due to this concept Allah brought the creation into being, and due to this concept He created Paradise and Hellfire. Allah says in the Quran:
[Surah adh-Dhaariyaat (51):56]
“And I have neither created the Jinn nor humans except to worship Me.”
This is the belief which all the Prophets and Messengers called to, from Adam, the first Prophet, to Muhammad, the last messenger, may the Safety and Blessings of Allah be upon them all. Allah says:
“And we have not sent before you any messenger except that We have revealed to him that there is no deity that is worshipped in truth except Me, so worship and obey Me.”[Surah al-Anbiyaa (10):25]
The Meanings of LAA ILAAHA ILL-ALLAH:
There is no Creator of this existence except Allah.
[Surah al-An‘aam (6):102]
“Such is Allah, your Lord! Laa ilaaha illa Huwa (none has the right to be worshipped but He), the Creator of all things. So worship and obey Him (Alone), and He is the Wakeel (Trustee, Disposer of affairs, Guardian, etc.) over all things.”
There is no True Master and Owner present in this existence except Allah.
“Surely, His is the Creation and Commandment. Blessed be Allah, the Lord of the ‘aalameen (mankind, Jinns and all that exists)!”[Surah al-A’raaf (7):54]
No deity deserves servitude and worship except Allah.
“No doubt! Verily, to Allah belongs whosoever is in the heavens and whosoever is in the earth. And those who worship and invoke others besides Allah, in fact, follow not the (Allah’s so-called) partners, they follow only a conjecture and they only invent lies.”[Surah Yunus (10):66]
All the Names and Attributes of Allah are perfect and complete.7 He is high above and free from all faults and shortcomings.
Allah () says:
[Surah al-A’raaf (7):180]
“And (all) the Most Beautiful Names belong to Allah, so call on Him by them, and leave the company of those who belie or deny (or utter impious speech against) His Names. They will be requited for what they used to do.”
So, here was a little description of the meaning of LAA ILAAHA ILL-ALLAH. Learning more about Islamic Theology will help you understand the concept more.