A public limited company differs from the private version in that it is able to sell its shares to the public, and may be quoted on the stock exchange or alternative investment market etc. A public company must satisfy Companies House that at least £50,000 worth of shares has been issued before it is entitles to begin business or borrow money, and two directors must be appointed.
The cost of running a public limited company are considerably higher, and so this form is better suited to large organisations.
Natwest is an example of a public limited company (plc).
As are nearly all banks and any other company on the FTSE 100