What does belief in Allah mean?

It means to believe in the existence and oneness of Allah and to know him very well through His names and attributes. Belief in Allah is the base of all religions. The need to believe in Allah, to rely on Him and to worship Him is inherent in the nature of man. That feeling was born together with man and continued in each period.

It is one of the evidences of the existence of Allah. For, the nature of man does not tell lies. Since there is a need to believe in and rely on a sublime Creator, to worship Him and to supplicate Him and receive what one needs from Him, then, it is impossible for that sublime Creator not to exist. It will mean to deny the nature of man. Even if there are no other evidences, this evidence of creation and conscience is sufficient light to understand the existence of Allah.

As a matter of fact, those who dare to deny Allah, have to turn to Allah and ask His help when they are in trouble. However, as soon as the trouble is over, they return to their previous state.

You probably saw and heard a lot of examples regarding the issue. That issue is pointed out in the Glorious Quran as follows:

“ When trouble toucheth a man, he crieth unto Us (in all postures)― lying down on his side, or sitting or standing. But when We have solved his trouble, he passeth on his way as if he had never cried to Us for a trouble that touched him! Thus do the deeds of transgressors seem fair in their eyes.)” (Yunus, 12)

“ Now if they embark on a boat, they call on Allah, making their devotion sincerely (and exclusively) to Him; but when He had delivered them safely to (dry) land, Behold, they give a share (of their worship to others).” (al-Ankabut, 65).