Al-Baqara question to anyone who might have an idea.

I am reading the english translation (translated by Yusuf Ali) of the Quran for the first time. I don't exactly have anyone who I can physcially talk to when it comes to my questions. In the 22nd ayat, it says, in the translation: "then set not up rivals unto Allah when ye know (the truth)". I'm just curious as to what Allah (SWT) means by setting up rivals. If that makes any sense please let me know, and/or guide me in my search. Thank you.