Defamation is the communication of a falsehood that damages the reputation of someone.
If the defamation is recorded, especially in writing, in a permanent form, it is libel. This would include statements made by email and pictures.
“The newspaper was sued for libel by the CEO of the company for publishing false information about her share dealings.”
If the defamation is not recorded, but merely spoken and unrecorded, it is slander.
“It is currently being determined in the courts whether statements made on an on-line bulletin board are to be considered libel or slander, since they may be more like having a conversation in a bar.”