It's a type of sundae also known as a Knickerbocker Glory. From Wikipedia:
A knickerbocker glory is a layered cream sundae that is served in a large tall conical glass to be eaten with a distinctive long spoon, particularly in the British Isles.
The knickerbocker glory, first described in the 1920s, may contain ice cream, cream, fruit, meringue. Layers of these different sweet tastes are alternated in a tall glass and topped with different kinds of syrup, nuts, whipped cream and often a cherry.
Here's a recipe telling you how to make one. And here's a picture of one:
There seems to be a lot of disagreement on the internet over the precise origin of the term "Knickerbocker Glory". But according to our colleagues over at the English Language & Usage SE, specifically Josh61 and Hot Licks (may upvotes rain down upon them and the site be ever in their favour), the most likely explanation as to the origin of the term "Knickerbocker Glory" is the following:
It has no connection with nether garments; the term was presumably inspired by Diedrich Knickerbocker, the mock-Dutch name invented by Washington Irving for the fictitious author of his History of New York. This subsequently became synonymous with the descendants of the original Dutch settlers in New Amsterdam, and eventually with New Yorkers in general - so a knickerbocker glory is essentially a tribute to New York. The term is first recorded in the 1930s.