2D Filters: Kernels?

I honestly have not the slightest idea what a “kernel” is in Blender’s GLSL scripts, but I see it a lot, so PLEASE, would someone explain these to me? Sorry about this. Gotta learn. Thanks!

From wikipedia:
“In image processing, a kernel or convolution matrix is (usually) a small square matrix used for smoothing or sharpening purposes. This is done by calculating the convolution between an image and a kernel.
A kernel is created by defining weights of neighbor pixels to a center pixel. The product of weights and pixel values are then summed up to find the new value of the center pixel.”

Here are some examples from The Gimp (2D image manipulation program):

For 2D filters I usually see these as 3x3 matrices.

Oh… So you could essentially draw around a specified pixel, rather than only affecting that individual pixel, then? That’s awesome! Thank you!