Do android phones automatically download photos

By that I mean I recently backed up my phone to laptop. When I went through the photos I came across several I had not taken. Some I recognised as friends photos that had been on facebook and I might have liked but definitely didn't download. Others were people I did not recognise. When I googled I found something about WhatsApp downloading it's pictures and have turned that off but I know that is not the culprit.

I use viber on android and any photos posted in conversations are saved to a folder in my photo gallery.

Thanks gipimann I came across that and have unclicked the automatically download for that and WhatsApp. Facebook only seem to have something to sync your photos from your phone which was off anyway. This is where photos are on my phone and I have no idea where they come from but suspect facebook. I don't even know some of the people in the photos and some of them are kids which is worrying. They are not stored in my gallery either and don't know where on the phone they are to delete them!

There is an app called quickpic which sorts all your photos into Viber,Facebook,camera,WhatsApp,downloads,etc etc.
It should be easier to see where the photos are coming from then.