BIP158 refers to a Bitcoin Improvement Proposal focused on a method for light clients to efficiently request and verify transaction data. This is particularly useful for wallets that want to operate without downloading the entire blockchain. The main feature of BIP158 is the ability to filter and request specific transactions from full nodes using compact filters.

Instead of downloading the entire block, a light client can ask for transactions relevant to its wallet while receiving proof of their presence. This approach significantly reduces the amount of data transferred and speeds up the verification process. BIP158 relies on a feature called “filtering,” where a light client generates a filter based on the transactions it is interested in.

Full nodes can then respond with the relevant data or a notification if the data is not present. This method aims to enhance privacy and efficiency in how light clients interact with the Bitcoin network, allowing users to maintain a balance between security and resource consumption.