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# Smart Contract Platforms
Smart contract platforms serve as the foundation of DeFi. In effect, they operate as the computers that run all of the applications listed above. So every time that you make a trade on Uniswap or lend money on Aave, you need to use (and pay) Ethereum.
Keeping with the ethos of DeFi, smart contract platforms are decentralized and distributed, meaning that they aren’t controlled by any one party, they can never be shut down and anyone can use them at any time.
I won’t go into too much detail on smart contract platforms here as, given their extreme importance, I wrote another 10,000+ word article on them, but I will highlight some of the important players in the ecosystem.
Source: Defi Llama as of 3.13.22
As of early March 2022, the largest smart contract platforms by Total Value Locked (a proxy for how much capital is “in use” in the ecosystem) are Ethereum, Terra, Binance, Avalanche and Solana. These five players represent over 80% of the market.
Market share as of 3.13.22
Once again, smart contracts platforms are not only extremely important to DeFi, but serve as the foundation for Web3, NFTs, the metaverse, decentralized gaming, DAOs and the decentralized economy as a whole. As such, I’d highly recommend learning more via this article, which dives into how they work, why they are important, who the key players are, how they stack up against one another and what’s next for the space.
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