There was a post in the past with exactly same query. Click the following link to refer it:
Anyway let me elucidate further. The word memo is derived from the word memorandum. The dictionary meaning of this word is a written proposal or reminder. Letter written by an government official called as memo. Nevertheless, in the Indian context the word memo has negative connotation and often it is used in lieu of warning letter or even a show cause notice. In the private sector, generally the word memo is not used.
The dictionary meaning of warning is a cautionary advice. Warning letter itself is considered as punishment for minor misconduct and it is a precursor to a disciplinary action if the misconduct is repeated. However, if the warning letter is issued, explanation is not sought from the employee. There could be a case that employee was issued with show cause notice and if the explanation of the employee was not found satisfactory, cautionary advice in the form of a letter is given.
Show cause notice is issued to an employee to seek explanation on the alleged misconduct. Show cause notice is issued when there is sufficient evidence of misconduct at hand or culpability of the defaulter is established in the enquiry. Issue of show cause notice is consistent with principles of natural justice and accused employee is given opportunity to come out with his/her defence.
From India, Bangalore