Halal is an Arabic term in Islam which means permissible, allowed. Its antonym is Haram.
According to the dietary rules of Islam, halal refers to the foods that are fit for Muslim consumption.

Muslims are allowed to eat the meat of animals that were properly, as per Islamic Practice, slaughtered.

With the exception of fish (both shell or non-shell where Allah's name is mentioned before eating), Muslims will only be allowed to consume the meat of the aforementioned animals if:

1. They are slaughtered by a believer in Allah
2. At the time of slaughter the slaughter man recites, “I the name of Allah and Allah is the Greatest,” or at the very least, “In the name of  Allah.”
3. With a very sharp knife the slaughter man manually swiftly cuts the oesophagus, trachea and the two jugular veins of the animal in a single cut. In the event of him being unable to cut all four he must cut at least any three of them.
   

Muslims are also not allowed to have any intoxicants such as alcohol nor any blood.

 

WHY IS HALAL IMPORTANT TO MUSLIMS?

Halal is important to Muslims because it is a divine dictate. Allah has issued the following orders in the Holy Qurʾān:
• “Mankind, eat whatever on the earth is lawful and good, and do not follow the footsteps of Satan. Indeed, he is a clear enemy to you.” (Chapter 2, verse 168)
• “Messengers, eat from the good foods [We have provided you] and perform righteous deeds.” (Chapter 23, verse 51)
• “You who believe, eat from the good things We have provided you and be grateful to Allah […].” (Chapter 2, verse 172)
• “So eat of that [meat] upon which Allah’s name has been taken, if you are believers in His verses.” (Chapter 6, verse 118)
• “And do not eat of that [meat] upon which Allah’s name has not been taken, for indeed, it is a grave sin.” (Chapter 6, verse121)

At the End, Allah Knows The Best and we ask for his forgivness if we error.