The Seven Deadly Sins are sins that characterize fallen humanity, so classified by traditional orthodox Christianity and especially held to, and taught by, the Roman Catholic Church since the early Middle Ages. Protestants would agree that the seven vices on the list are sins, but generally don't make a distinction between mortal and venial sins in the same way Catholics do.
The Seven Deadly Sins in the Bible
The Bible includes lists of sins, though none align exactly with the traditional "seven deadly" sins.
In the Old Testament, Proverbs 6:16-19 reads,
“These six things doth the LORD hate: yea, seven are an abomination unto him: 17 A proud look, a lying tongue, and hands that shed innocent blood, 18 An heart that deviseth wicked imaginations, feet that be swift in running to mischief, 19 A false witness that speaketh lies, and he that soweth discord among brethren.”