Looking at an English article online, I can often tell straight away that it was written by AI. There are a few reasonably obvious tells.
Three common signs
Long dashes. AI uses them constantly, far more than most human writers do.
Short, clipped sentences. A run of very short sentences one after another, which reads slightly jerkily. If you are not used to it you will not notice, but anyone who uses these tools a lot spots it immediately.
Semicolons. They turn up in places where an ordinary writer simply would not reach for one.
Why this is worth noticing
Not in order to look down on the writing. It matters because when you read English in order to learn, you need to know what you are reading.
An AI-written piece is not the most natural model to imitate. Absorb your phrasing from it and you are learning a slightly mechanical voice.
One more thing to recognise
Plenty of articles look like personal experience, someone describing how they learned Spanish, say, but exist to advertise a product at the end.
English has a word for this: advertorial, from editorial and advertisement. A piece that looks like genuine content but is there to sell something.
Once you know the word, you start seeing that format everywhere, and you read it differently.