Can somebody explain to me about rennet?!

Rennet is enzymes from the lining of the stomach of the baby of the species you're using the milk from to make cheese. It helps the milk coagulate or curdle because it's enzymes that help a baby to digest mama's milk. If you have cheese from cow milk, the rennet comes from the calf's stomach as a byproduct of the veal industry. The veal industry is supported by the dairy industry, because cows are impregnated about once a year to keep them producing milk. Their babies who would naturally drink the milk are taken from them. That's where veal comes from. Baby meat. This is why it makes little difference to the baby if you're eating rennet or eating dairy products. The baby is killed in either case, and one of the reasons I don't use dairy.

There are cheeses made without rennet that use microbial enzymes.

Rennet is a bi-product of slaughter that is used to make some cheeses. It is my understanding that it is crushed bones.
I did not know about it until after I'd given up years of lacto-ovo vegetarian diet to be a vegan. So the entire time I was a vegetarian, I was eating cheese everyday. Who knows how much rennet I had.
It is good you found out much sooner!

as a new vegetarian and are keen to learn, please also look at this site for more food additives that you might not realise are not suitable. I printed it off and carry it everywhere I go, just in case I need to check a number. Good luck.

http://www.veggieglobal.com/nutrition/no…

Calf rennet is extracted from the inner mucosa of the fourth stomach chamber (the abomasum) of young, unweaned calves. These stomachs are a by-product of veal production.

http://en.wikipedia.org/wiki/Rennet

Rennet is from slaughtered cow stomachs. It helps curdle the cheese I believe. Of course some cheese brands use a vegetable rennet. Pretty much anything with cheese in it.

rennet is acid from a cow stomach, used to coagulate milk to make cheese.

Many brands use non animal rennet. But some don't.

This may be a kind of food additive, you trust, the human body without damage.