in Spades, playing King over Queen
You got had! Nice play by your opponent (South).

Terminology:


A finesse is the play of a lower card than the highest held - in an attempt to create an extra trick - by the third hand playing to the trick.
South on this hand employed a ruse to create the extra trick by leading the lower card (Queen from holding topped by just Ace-Queen).


There are Game Theoretic issues with a second-hand holding such as your holding here of Kx - where it is important to not be predictable. I suspect that you, and possibly North as well, have become predictable in your play with short Spade holdings.



Comments being ephemeral, and all that, two comments of mine from below are saved here:


I cannot imagine any strong, or better, Contract Bridge player not regularly leading top of an interior sequence, or second lowest, to see how many errors can be induced by the opponents. I do it regularly. South in this case seems to have a similar low regard for the card skill of his opponents. (Bridge players are snobs about the card skill of Spades, Hearts, and Euchre players - for very good reason.) If you are serious about improving your card play at Spades, and other trick-taking games, learn and study Contract Bridge and its associated play.
A good starting resource is the web site run by multiple National ACBL Championship winner Richard Pavlicek and his son: rpbridge.net/rppt.htm