Is the use of someone else’s words and claiming them as your own

No, and yes.

Explanation:

If you citing them for like an essay and use quotation marks thats not claiming them as your own, your just using then to cite evidence. Now, if you were to not use quotation marks then yes, it is claiming the words as your own. Also, if you look something up or its from a book, etc as long as you paraphrase your fine. If you don't paraphrase then that is claiming the words as your own. I hope this helps! have a good day :)