0x3dbb202b?0x3dbb202b is the function selector for sendMessage(address,bytes,uint32). Sends a cross-chain message.
When a transaction's data begins with 0x3dbb202b, it is calling sendMessage. The selector is the first four bytes of the keccak-256 hash of the signature sendMessage(address,bytes,uint32), which is how wallets and explorers work out which function a payload is for.