Why the dataset looks like optical images

[PalgunaGopireddy]

Hi. I know this repository concerns the remote-sensing images. As a person researching in remote-sensing , I have a doubt. I have seen the images in the figures of NWPU-RESISC45 dataset and AID dataset.

What I do not understand is, they look like optical images. Even the images in the NWPU-RESISC45 dataset paper Figure 1 are showing shadows for the trees. If these are they should not have any shadows. Are there really remote-sensing images?

Are they saying by remote-sensing means they are optical images taken from very-much distance like aeroplanes and satellites? , not concerning radar images.?