as no user have any permission to read file.txt,then why/how ‘sudo cat file.txt’ prints file contents?

bs01316@bs01316:~/test$ ls -l
total 4
---------- 1 bs01316 bs01316 6 মে        7 16:20 file.txt
bs01316@bs01316:~/test$ sudo cat file.txt 
hello

is superuser & root user samething or different concept?