Fiends and friends are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Fiends is a plural noun. A fiend is an evil creature, like the devil or a possessed person. It can also describe someone who has an intense interest, an exceptional talent, or an addiction.
Friends is a plural noun. Friends are people that voluntarily connect with each other and have an emotionally supportive relationship. Typically, friendships start over common experiences or shared interests.
The following story uses both words correctly:
Feleti was about to start school in a new town. He was a soccer fiend. He loved to play in the woods, and he loved to eat vegetables. When he started school, his parents were worried he might have a hard time making friends.