Three logos: LibreOffice, IBM by Paul Rand and the International Bureau of Weights and Measures.
A logo is a graphic mark or emblem commonly used by commercial enterprises, organizations and even individuals to aid and promote instant public recognition. Logos are either purely graphic (symbols/icons) or are composed of the name of the organization (a logotype or wordmark).
In the days of hot metal typesetting, a logotype was a uniquely set and arranged typeface or colophon. At the level of mass communication and in common usage a company’s logo is today often synonymous with its trademark or brand.
from :www.wikipedia.org”