iPhone photos are showing up on my mac library

I do not want my iPhone photos showing up in my photo library on my mac. I'm going to assume this has something to do with iCloud? I don't want my photos showing up so everyone in my family who uses the computer, sees my business. And I also have all my photos from my computer, in my phone. All 22k photos. I'm not tech savvy, so talk to me like I'm 2yrs old.