Why ./home/Desktop is incorrect and ./Desktop is correct?

I'm learning about Linux, started yesterday. I have a question which I couldn't answer from my book or Google. What is the difference between ./ and / in the shell? I'm asking this because when I run, for example, the command ./home/yogesh/Desktop/Books, I get this error: bash: ./home/yogesh/Desktop : No such file or directory However, on removing the dot it gives /home/yogesh/Desktop/Books : Is a directory Or, if I run /Desktop, it returns /Desktop : No such file or directory But on adding a dot before /, I get ./Desktop: is a directory What is the difference between ./ and /?