What are Kanban Cards and how do they work?

When trying to implement ‘Just in Time’ manufacturing it became clear that we needed some type of visual communication strategy that would make it easy to bring supplies where they need to be. The Kanban system seems like a great solution to this problem but haven’t actually put it in place yet. When using Kanban, how are the Kanban cards used?
Are there different Kanban cards for each type of supply? Are they all the same? Looking for more information on these before moving forward with implementation. Thanks!