Arbitrum is a Layer 2 network built to help Ethereum handle more activity at lower cost. Instead of processing every transaction directly on Ethereum, it handles them separately and posts summarised results back to the Ethereum base layer, easing congestion and reducing fees.
It uses a technique called optimistic rollups, which bundle many transactions together and assume they are valid unless challenged within a set window. This lets Arbitrum offer faster, cheaper transactions while still relying on Ethereum for underlying security.
This entry explains what Arbitrum is and how it fits into Ethereum scaling. It is educational and describes the technology role. It does not evaluate any associated token as an investment or recommend any action.