As you know Bitcoin, Ethereum and Solana differ in several things as the blockchain architecture, wich is proof of work for BTC, proof of stake for ETH and proof of history for SOL. ETH and SOL can use smart contracts wich permit several use cases.

Smart contracts

As said ETH and SOL can handle smart contracts, thereby can be used for decentralised apps, although ETH is at the moment more popular.

This opens up to:

Defi: decentralized finance
NFT: non fungible tokens
decentralized applications and gaming

solana transaction are faster, and fees cheaper.

Ethereum is commonly used for defi, gaming and nft,
Solana for high-speed transactions, trading, gaming, and other things that require faster and cheaper transactions.

Transactions and fees

BTC
3-7 transactions per second average
average 0.000044 satoshi transaction fee

SOL
2.825 transactions per second average
average gas fee 0.0001 SOL for transaction

ETH
15-25 transactions per second average
average gas fee 0.0026 ETH for transaction