It's easy to look on Google Images and find an image that matches your content. But is it safe to use those images on your website? The short answer is "No it is not . You never know who owns the copyright of the image. If you use an image or photo without permission of the owner of that photo, that is called copyright infringement.
What can you do to find an image owner
Sometimes a photo or image has a watermark, in other cases an owner might have added his name or website name to the photo so that you can find back the legal owner of the image or photo. It's possible that the owner has added an "alt tag" to the image or photo. You can find the alt tag by hovering over the image. More often there will be no watermark, tag, url or name of the owner.
In that case you can use Google Images, you can upload an image or photo and find the original creator of the image or photo and pay for a license to use it on your website. If you cannot find the legal content owner that doesn't mean the image is royalty free, you still cannot use the image on your website if you do not know the image owner.
Social Media and Images
You might ask yourself the question why can't i share all photos on my website? Because pictures and photos are shared on Facebook, Twitter, Pinterest, Instagram and other Social Media. It's ok to retweet pictures other people have posted. It's even ok to save them on your pc, just do not use them on your own website. If you use them on your own website you can be accused of copyright infringement and you can get a claim and you can get sued by the press agency (or a company that represents them) that owns the photo. It doesn't matter if you own a commercial or non commercial website.
A famous known company that sends out claims which are called "Settlement Demand Letters" is Getty Images. But that is just one of many companies another company that is located in Belgium is called Permission Machine. Permission Machine works the same as Getty Images. They send a claim, which you are forced to pay, you can refuse, but if you do they will take your case to their lawyer. And if they win the case you can pay for the additional costs.
What do i recommend: for website owners
It's better to be safe than sorry. If you make an article, you could better make your own photos and have original content on your website than use the content that is owned by someone else. If you do not want your image to be used by someone else use a video instead. If you own an image gallery be sure to look carefully who owns the rights of the images. If you are not the owner of the images and do not know who the image owner is, i recommend to take the gallery off your website. It's better to be safe than sorry. it's better to take off your gallery before you get a claim than to regret it later on after you receive a claim.
Video is more lively than a photo is and if you have a YouTube channel you can earn money because YouTube will show advertisements while people are watching your video. As a result of having the video you will drive more visitors to your website because you have videos on YouTube. And you can share the video in social media as well and other website owners can place your video on their website -which will make you extra money!