Can anyone explain me the write permissions in ubunto terminal?

Question

read write and executable represented by numbers

Answer 1

they are what they say. read,write and execute permissions. the numbers represent to whom the permissions are given to.

Answer 2

read has the value 4
write has the value 2
execute has the value 1

so You can calc which rights u want to give for the owner, groupmembers or anybody...

so "chmod 750 somefile" defines the permissions rwx for owner r-x for groupmembers and no rights for others (somefile rwxr-x--- )