A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but it can
a) give out a force that pulls on other magnetic materials like iron and steel
b)attract or repels other magnets.
Below is a video that shows two magnets repelling from each other. No matter how hard you push the magnets towards each other, they will never ever stick!
The second video shows how two magnets attract the iron fillings inside the glass cylinder.