Halalan toyibban merely means allowed and permissible for consumption with relation to Syariah law as long as they are safe and not harmful. The opposite of Halal is Haram / non-Halal that means forbidden and prohibited. Any food or drink which lies within the grey area and does not fall clearly under the Halal or non-Halal category is classified as Syubhah', alternatively called questionable or dubious. In this category, until the status becomes clear, Muslims should avoid consuming Syubhah food or drinks.
The general principle concerning food according to Islamic teachings is that everything is Halal except impurity (or mixed with impurity), harmful and intoxicant. Therefore, it is compulsory for Muslims to eat good and healthy food and to avoid all that is forbidden by Allah.
Malaysia has defined Halal food through its MS1500:2004: Halal Food – Production, Preparation, Handling & Storage – General Guideline (First Revision) as food permitted under Shari'ah and fulfills the following conditions:

