Saccharin is 300 times sweeter than regular sugar and is often recommended to diabetics and slimmers. Sold in tablets and granular form it is most commonly used to sweeten beverages.
It can be used in cooking also however great care must be taken as too much will give a bitter taste.
And yes, it is manufactured from coal tar. Coal tar is a thick, dark liquid that is a by- product of processing coal into coke and coal gas.