Merchants
Who you paid. Default categories that make new transactions categorise themselves, and the merchant spend report.
A merchant is the other party: the supermarket, the landlord, the streaming service. Bank imports carry a raw description that is rarely a clean name, so Walletguide resolves it to a merchant you can then treat as one thing.
Default categorisation
The reason merchants earn their place. Give a merchant a default category and every transaction from them afterwards arrives already categorised.
You can also apply that default retroactively to transactions already in the wallet, which is the fastest way through a first import: set the merchant once, apply, and a few hundred rows sort themselves.
Spend by merchant
The merchants view lists them with how many transactions and how much each has taken. It is the most direct answer to "where is the money actually going", and it pairs with the recurring report for finding subscriptions you had forgotten.
Merging
Two merchants that turned out to be the same shop merge into one; the transactions move and the duplicate goes. Not reversible.