Spelled "trademark" in American English, as two words in England, Australia and Japan ("trade mark"), and with a hyphen ("trade-mark") in Canadian English.
Trademarks are a form of intellectual property and thus, monopolies granted by the Government and enforced by the Courts to traders or mechants reserving words, slogans, names or symbols (logos) or, in some jurisdictions, sounds 
(jingles) or colors (Australia will even allow the trade-marking of a smell), that are used to mark and distinguish the merchant's goods or services from those of others.
Well-known trademarks include the Coca-Cola and McDonald's logos.
The trade-mark of the Victoria, British Columbia law firm of Duhaime Law is pictured.