It is one that lets you accept card throughout your premises and is known as a Bluetooth and it sends information between the cradle which then uses Ethernet or Phone line.
The majority people who use this type of machine are cafes or bistros which need this sort of machine since they must allow people use cards while sitting at the tables, however, it can be for other purposes.
The kind which is mostly for the person who must take cards on the go and is called a mobile one, this only needs a connectivity with a network. It can be taken outside so you can take card across the United Kingdom and you will not require a landline.
Last but not least is a desktop that is for those who need to accept card in certain areas next to power point and a internet or phone connection.