What Does Halal Mean?
Halal is an Arabic word meaning permissible, legal, or allowed. For Muslims, the word Halal is specifically used to identify the practices, actions, and statements that are legal and permissible. Everything a Muslim does, from the food we eat to the way we worship, must be Halal.
The opposite of this word is haram, any action that is deemed impermissible for a Muslim to perform.
Generally, any action in this world in this world is halal, or permissible, by default unless there is a verse of the Qur'an or a hadeeth of the Prophet (peace be upon him) saying otherwise.
For example, in the beginning of Islam a Muslim could drink alcohol until the following verse was revealed:
O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone alters [to other than Allah], and divining arrows are but defilement from the work of Satan, so avoid1 it that you may be successful.Qur'an - Chapter 5: Verse 90
With this verse, Muslims know that it is haram to drink alcohol.