A portable keyboard means a keyboard with easy portability. Portable keyboard is not a specific name for a certain keyboard. It is, in fact, a series of keyboards. To sum up, there are mainly four types of portable keyboards:

Roll-up keboard or roll keyboard

A roll-up keyboard is a rubber made, easy to fold, portable keyboard. A roll-up keyboard can be put in a plastic tin when it is rolled, making it quite easy to carried away.

Foldable keyboard

Foldable keyboard means keyboard with foldable structure. Foldable keyboard is consisted of several separated metal plates, which can be folded and packed. A foldable keyboard is quite a ideal accessory for notebook, especially when taken along when you are on trip.

Roll-up keyboard or foldable keyboard can also be called flexi keyboard, flexible keyboard or folding keyboard because of their foldable feature.

Numeric keypad
Numeric keypad is small size and with USB plug. The wire of numeric keypad is often made retractable, making it a good a accessory for notebook and quite a portable input device.

Mini keyboard

Mini keyboard is mainly used on iPhone or iPad. The size of mini keyboard is usually just like that of your palm, making it so convenient to take along with you.