What is difference between trademark and logo?

Answer 1

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).

A trademark or trade mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or services from those of other entities.

A logo may be a trademark.

Answer 2

They're the same thing: a mark used in trade to identify a product or service. The word "trademark" however is more frequently used these days to refer to the law protecting logos, slogans, etc. You might also have a logo not specifically used in trade.