If you've made it this far, you're probably familiar with the semi-addictive word game Wordle. (If not, just DuckDuckGo the term "Wordle" and prepare for a life-changing experience). So I'm going to assume that you're familiar with the game, and that you're here to learn how to use this Wordle8r tool/toy.
Start Wordle as you normally would. Make your first guess. Then, when you get feedback, enter the same guess into Wordle8r and the feedback (colours) that you received from Wordle. Wordle8r will then generate a list of possible words that could be your solution word. You can then use this list to help you make your next guess. Should you need help... Repeat as necessary. Easy peasy.
Of course, this may be considered cheating by some! And, yes, it is a good mental and vocabulary exercise to solve the puzzle without any help. But, if you're stuck, or if you're just curious, this tool is here to help. (I haven't used it myself this way—although I was very seriously tempted recently when a streak of 89 was on the line—it was more of a fun programming exercise. But I do use it after the fact to see what I missed.)
Wordle uses two word lists. The first is a list of all five letter words, as determined (I think) by the Scrabble word dictionary. Many of these more than twelve thousand words are quite obscure: abmho, becke, caple, dashi, ... But they are all legal and Wordle will accept them for a guess.
Wordle won't use these obscure words for a puzzle answer, though. The second list—of around 2,300 more 'common' words—are used to choose the word of the day, in random order. Or that was how the original version of Josh Wardle's game was designed; now that it is owned by the New York Times, the original answer set has changed a little. For example, the word "squid" was the NYT answer recently despite never being one of the 2,300 or so of Josh Wardle's original answers.
When you look at the list of possible words for the current state of your guesses, you may notice some in bold font. These represent the words originally in the answers list. For the most part, it still represents the set of possible answers. "squid" and an unknown number of other words notwithstanding.