A monogram is a motif made by overlapping or combining two or more letters or other graphemes to form one symbol. Monograms are often made by combining the initials of an individual or a company, used as recognizable symbols or logos. A series of uncombined initials is properly referred to as a cypher and is not a monogram, although ciphers are frequently referred to as monograms.
An individual's monogram is often a very fancy piece of art for adorning luggage, clothing, and so forth.
Monograms of the names of monarchs are used as part of the insignia of public organizations in kingdoms, such as on police badges. This indicates a connection to the ruler.
Monograms like the interrobang are used as letters, punctuation, and the like, and are not used for companies.