Distribution counting notation understanding problem

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It's hard to ask good question about it but I have problem with understanding notation which is as follows:

$$p(y\mid x, κ) = \frac 1 κ \sum_{i∈N κ(x, D)}\mathbb{I}(y_i = y)$$

The aim of this equation is to model probability distribution $y$ for given $x$, with given $k$? where $k$ is number of nearest neighbours. If u could help understanding what exactly that sum notation is ;/ Do I need to sum multiplications of identity matrix's multiplicated by some $y$?
Sry for my poor knowledge.
Thanks in advance