In America we call them zip codes. They are 5 digits long. They are normally read in one long series, not 23 45 13, etc.

British English: Postcode please? American English- Zip code Please?

In the UK they're called 'postcodes', yes. They are either six or seven characters long and a combination of letters and numbers. The code is normally split in two, there is a three or four character section, followed by another three character section. For example, the postcode of Buckingham Palace is SW1A 1AA. If you want to know someone's postcode, for example, if you want to use something like Google maps then 'what's your postcode?' is what you would ask in the UK. As has been mentioned the terminology varies slightly from place to place.

I believe in other English speaking countries they are called postal codes. In Canada they are a combination of letters and numbers, usually six altogether