TL;DR
A Solana validator is a server that processes transactions, produces blocks, and participates in consensus to secure the Solana network, earning rewards from staking and transaction fees.
Validators verify and execute transactions, vote on the validity of blocks, and take turns as “leader” to produce new blocks. When a validator is the leader, it orders pending transactions into a block and broadcasts it. Other validators verify and vote on that block. The more stake delegated to a validator, the more often it gets selected as leader and the more influence it has in consensus.
Validators earn from three sources: inflation rewards (new SOL minted each epoch, distributed proportional to stake), transaction base fees (50% of fees go to the leader), and MEV rewards (Jito tips from bundles). They share inflation rewards with delegators after taking a commission. Running a validator costs $500-2,000+/month in server costs, so they need sufficient delegated stake to be profitable.
Validators directly affect your trading experience. When you send a transaction, the current leader validator decides whether to include it and in what order. Jito validators accept tip-paying bundles, enabling priority inclusion. Validator performance (speed, uptime) affects network reliability. The geographic distribution of validators affects latency for traders in different regions.