Lying is a vice of deliberately being untruthful and deceitful. It is a false assertion made to deceive someone.
Lie has a negative connotation and depending upon the context a liar can have social, religious or legal sanction.
On the ethics of lie, the views of scholars diverge.
A deontologist will say that lying is unethical in every situation. For a utilitarian lying may be allowed if it leads to greater happiness for greater number.
Further a consequentialist may argue that ethics of lying will depend upon the context and situation