An insider is someone who belongs to a group and knows things that outsiders don't. In a company, insiders might know about new products before they're announced to the public. At your school, student council insiders know what the next spirit week themes will be before the posters go up.

The word often describes people with special access to information or power. A political insider knows how decisions really get made behind closed doors and understands the relationships and deals that shape policy. A Hollywood insider understands which movies are being filmed and which actors are being considered for roles.

Sometimes insider carries a hint of exclusivity or secrecy. When friends develop inside jokes or a secret handshake, they've created their own insider knowledge that bonds them together. But the word can have a darker edge: insider trading is when someone illegally uses private company information to make money in the stock market, which is why laws exist to prevent it.

The opposite of an insider is an outsider, someone looking in from the outside who doesn't have the same access or understanding. Being an insider means you're part of the inner circle, whether that's your school's robotics club, your family, or any group that shares knowledge and experiences that others don't have.