It's called an interrobang, and it's meant to represent both a question mark and exclamation point at the same time:
: a punctuation mark ‽ designed for use especially at the end of an exclamatory rhetorical question
Did You Know?
Most punctuation marks have been around for centuries, but not the interrobang: it's a product of the 1960s. The mark gets its name from the punctuation that it is intended to combine. Interro is from "interrogation point," the technical name for the question mark, and bang is printers' slang for the exclamation point. The interrobang is not commonly used—its absence from standard keyboards can explain its paucity in print perhaps just as well as its paucity in print can explain its absence from standard keyboards. Most writers who want to communicate what the interrobang communicates continue to do as they did before the advent of the mark, throwing in !? or ?! as they feel so moved.
Also from Wikipedia:
The interrobang (/ɪnˈtɛrəbæŋ/),also known as the interabang (‽) (often represented by ?!, !?, ?!? or !?!), is an unconventional punctuation mark used in various written languages and intended to combine the functions of the question mark, or interrogative point; and the exclamation mark, or exclamation point, known in the jargon of printers and programmers as a "bang". The glyph is a superimposition of these two marks. The interrobang was first proposed in 1962 by Martin K. Speckter.
Its use is nonstandard and normally only used in informal text.