Late Bottled Vintage port is from a single year. The wine ages 4-6 years in old oak casks (opposed to Vintage that ages 2-3). LBV fills the gap between the rubies and the vintage ports since a Ruby Port should be drunk quite young and a great Vintage Port may need 15 to 20 years to really open up and show its splendour.
This led to the idea in the 1960s to age the wine 4 to 6 years in large casks before bottling it, thereby producing a wine with the style of a Vintage Port with its deep colour and concentration of fruit but with a more mature character caused by the longer ageing in wood. This particular vintage is from 1986, which was bottled in 1990.