How the best-guess suggestions work
When several words still fit your pattern, the smartest move is to guess a letter that appears in as many of them as possible. The solver counts, across all remaining candidate words, how many contain each unguessed letter, then ranks those letters and shows the percentage of words each one appears in. A letter in ninety percent of candidates is a near-certain hit; one in twenty percent is a long shot.
This frequency approach does two things at once: it maximises your chance of revealing a letter, and when the letter is present it usually splits the remaining words into a much smaller set. That is why the top suggestion is almost always your best play, especially early in a round when many words are still possible.