A “Legal Notice” is a legal intimation sent to the opponent indicating that the aggrieved is preparing to file a lawsuit against the concern in case the demand mentioned in the relevant notice is not fulfilled.
Therefore, in a nutshell a legal notice can be defined as a formal communication to any person or a legal entity, informing the other party of your intention to undertake legal proceedings against them.
This notice, when sent, conveys your intention prior to the legal proceedings and thus, makes the party aware of your grievance.