How to find out the structure of a directory?

Question

linux

In general, there is a folder with subfolders with photos .
I made ls -lR dir/ | grep "^-" | wc
it. It showed that there are 119343 photos.
How can I find out what extensions are there (jpg, png or something else)
And how can I find out the maximum nesting depth?

Answer 1

View statistics for extensions

find ./dir/ -type f | awk -F . '{print $NF}'  | sort | uniq -c | sort -nr

Look at the structure - for example, through
tree -d ./dir/

Answer 2

find /path/ -name "*.png" | wc -l