A security is a tradable financial asset. They exist as a way for businesses and goverments to acquire money to fund their ventures and operations.
Securities are a type of financial instrument, which is a contract between parties that serves as evidence of an agreement or ownership over assets.
It’s called a security “because there is a secure financial contract that is transferable, meaning it has clear, standardised, recognized terms, so can be bought and sold via the financial markets,” (source).
Securities are divided into 3 categories mainly: