The sigil of Baphomet is a symbol that some people associate with a group called the Satanic Temple. It looks like a picture of a goat's head inside an upside-down pentagram. The goat's head has two horns, a beard, and a pentagon on its forehead.
Some people think this symbol is scary or evil, but others might see it as a representation of their beliefs or even as a kind of joke. The Satanic Temple itself says that the sigil is supposed to represent "the wings of compassion and the willingness to embrace rational inquiry" as well as "the triumph of the individual over dogma."
So basically, the sigil of Baphomet is a picture that some people use to represent their ideas about Satanism or their beliefs about individualism and questioning authority.