This and these 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.
This is a singular pronoun. It’s used to indicate one specific thing in relationship to other things. For example: This wet umbrella doesn’t look like the others with our logo on it. It probably belongs to that man who dashed out the door to take a call and never came back.
These is a plural pronoun. It’s used to indicate more than one thing, or a group of things, in relationship to other things. These is the plural form of this. For example: These clean clothes need to be hung up before you take a nap in this bed. Don’t just throw them on the floor.
The following story uses both words correctly:
This was the most exciting, eye opening year of Thenjiwe’s life thus far. These are days she will treasure forever. When she returns home, she will create a web journal of all the experiences she’s enjoyed as a foreign exchange student in Paris. Then she will start planning her next adventure.