Hi,
" To Whom It May Concern"- what does it mean? what purpose of this phrase?
It's a formulaic way of starting a letter or notice. It means 'this communication is intended for anyone that it has importance for.'
If you are writing to a person whose name you know, but instead you begin in this way, it sounds very rude and very aggressive.
eg To whom it may concern: If the rent arrears are not paid in full immediately, I will change the locks.
eg To whom it may concern: The undersigned will not be responsible for any debts incurred in his wife's name.
Best wishes, Clive