Magnets are appliances made of magnetic metals or alloys such as iron, nickel and cobalt, which have the characteristics of attracting iron, nickel and cobalt. "Snake and tiger with one knife" refers to a kind of martial arts skill, which is a kind of move in knife method and has the characteristics of quickness, accuracy and viciousness. There is no direct connection between the above two questions, and more definite questions are needed to provide more accurate answers.

　　Hello, a magnet is an object that can generate a magnetic field. It is usually made of magnetic materials such as iron, nickel and cobalt. It can attract iron, steel and other substances, and can change its magnetism through current.

　　"Snake and tiger fell with one knife" is not a common idiom or word, and its exact meaning cannot be determined. It may be a term or slang for a particular occasion or field.

　　The gyromagnet is a kind of material that can generate magnetic field and attract iron, nickel, cobalt and other substances. Magnets are composed of iron, nickel, cobalt and other substances. There are many unpaired electrons in the atoms of these substances, and these electrons constantly spin and produce magnetic fields to form magnetism. When a magnet is close to magnetic substances such as iron, nickel and cobalt, their magnetic fields will interact, and some of the electronic magnetic fields will be attracted to another substance. Magnets are widely used in various fields, such as motors, generators, speakers, magnetic storage devices and so on. At the same time, magnets can also be used in life, such as making refrigerator magnets and magnetic levitation toys. The meaning of "snake and tiger fell with a knife" is not very clear, and more context may be needed to give an exact answer.

　　The answer is as follows: a magnet is an object that can attract magnetic substances such as iron. Its principle is that because the magnet itself is magnetic, it will produce magnetic force when it is close to iron and other objects, thus attracting iron and other objects.

　　"A snake and a tiger fell with one knife" is an idiom, which means that we should take drastic measures to defeat the enemy with one knife. This idiom comes from the Warring States Period, when Sun Bin, the general of the State of Qi, adopted the tactic of "snake and tiger with one knife" and successfully defeated the enemy.