what is filter and kernel_size?
Filters are used to extract features from images in the process of convolution.


  filters: Integer, the dimensionality of the output space (i.e. the
  number of output filters in the convolution).
  
  kernel_size: An integer or tuple/list of 2 integers, specifying the
  height and width of the 2D convolution window. Can be a single integer
  to specify the same value for all spatial dimensions.


For detailed undestadning of filter and kernel_size, refer: 
https://www.saama.com/blog/different-kinds-convolutional-filters/ 
https://keras.io/layers/convolutional/