Captain Marvel, the big red, white, and gold costumed dude, is a character from Fawcett Comics. Young boy Billy Batson can turn into Captain Marvel by shouting “Shazam!” thanks to some mystic tomfoolery. DC sued the heck out of Fawcett in 1953 because they said Captain Marvel was a copy of Superman. In '72 DC started publishing some Captain Marvel comics by licensing the character from Charlton which had nabbed the rights from Fawcett. By '91, DC bought the whole catalog.
The funny part is that Marvel snagged the copyright to the name “Captain Marvel” in the 1967. DC published their Captain Marvel series under the title Shazam! which lead many to refer to the character as Shazam anyway. DC officially renamed the character Shazam in 2011 when Marvel started to really assert their ownership of the name.