That's adware, those ads popping up are trying to get you to click on a link to download something bad. They're either coming from some apps you installed, or a website you visited. Clear your browsers cookies, and if that doesn't work start uninstalling the apps you've recently installed until they go away.
Looks like you may have accidentally allowed notifications from a website (assuming a rogue app isn't causing this) when it requested permission. Easy to do if it pops up as you are about to tap something. Check your open tabs on Chrome to see if one or more are open from that website.