Plain meaning
Start with the shortest useful explanation before going deeper.
A client library that sends transactions directly to the current leader validator's Transaction Processing Unit (TPU) port over QUIC, bypassing the standard RPC sendTransaction relay for lower latency and higher landing probability. The Solana SDK's TpuClient resolves the current leader from the leader schedule, establishes a QUIC connection, and forwards signed transactions directly. This approach is used by MEV searchers, high-frequency traders, and latency-sensitive applications that need the fastest possible path to block inclusion.