Centralized exchanges (CEX) generally serve as the on and off ramp between crypto and your bank.

DEX and DeFi allow crypto holders to make money by borrowing / supplying needed crypto by various markets.

Users of decentralized platforms are often rewarded with significantly higher interest rates than CEX, "air drops" of NFTs and new coins based on the platform's needs.

The decentralized blockchain world is currently in an early adoption phase with exponential growth. If you are reading this, you are very early!