You’ll and yule 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.
You’ll is a contraction of “You will.” This phrase (and its contraction) describe the intentions or ambitions of someone else in the future, coming from a narrator/speaker who is talking directly to that person: You will lose weight on that New Years diet. You will enjoy that highly acclaimed movie. If the narrator were not talking directly to the person, they would say “She’ll/She will lose weight,” or “He’ll/He will enjoy that movie” instead.
Yule is a noun. It describes a pagan holiday that is celebrated around December 21-22. Yule recognizes the rebirth of the sun and the beginning of winter season. It involves burning a yule log, evergreen tree branch decorations, and other festivities. When Christianity began taking over Europe, many yuletide traditions were folded into Christmas season decorations and traditions.
The following story uses both words correctly:
Yolanda, a festivities historian, was often heard saying to groups, “You’ll not believe the number of people who think yule and Christmas are synonymous names for the same holiday. They are celebrated in the same month, but they are not the same holiday.”