A wildcard letter is a blank or unknown tile. In UnscrambleFlow, a question mark or asterisk can stand in for any letter, which means the tool checks many more combinations than it would with a fixed rack.
That is useful when you have a blank tile in a word game, a missing crossword letter, or a puzzle where one character is still uncertain.
Use a wildcard when one letter could be several different things. For example, searching for b?aker lets the tool test options such as baker, beaker and weaker-style patterns where the unknown position changes the possible word set.
Wildcards are also helpful when you are checking whether a blank tile can turn an average rack into a scoring play.
Every wildcard increases the number of possible searches. One wildcard is usually manageable. Two or more can produce a very broad list, especially with common letters. Use starts-with, ends-with, contains or exact-length filters to keep the results useful.
Start with the letters you know, add one wildcard, then narrow the result by word length. That is usually faster than adding several wildcards at once and reading through a long list.