International Driving Permits are required for many countries around the world. The IDP is a translation of your national driving licence and is only valid if you have both together. In some instances agreements have been made to allow the use of national driving licences unsupported by the IDP. This is the case in the EU. From the 28 Mar 19 this agreement with the EU will come to an end and the Vienna Convention Rules will apply. There are 3 conventions made in 1926, 1949 and 1968 and the type of IDP required to drive in a country depends on which convention that country has signed up to. Not all EU countries have adopted the latest 1968 version. For most countries the 1968 version will suffice but a few such as Spain require one of the others.
Full details can be found here including which countries accept which version.
International driving permits for UK drivers from 28 March 2019 - GOV.UK
The 1968 version can be obtained from Post Offices from 1 Feb 19. You need a passport photo, your original driving licence, ID and the fee of 5.50. The RAC and AA will cease issuing IDPs of any type after the 31 Jan 19