Defining your image with proper tags and title is known as image optimization. This helps search engines to know about your webpage image and rank them accordingly.
image optimization will help your site more friendly with google robot. that is part of on-page seo technique.
How to do that ? you have to let your keyword in alt tag and title of image.
Image optimization is using the most compressed (smallest file size) yet visually acceptable image in the proper file format for the specific role of the image.
Image optimization is the basic steps for your SEO campaign. One of the basic tips for image linking is to avoid linking your images directly. Always use relevant anchor texts whenever linking your images. This is even more effective for your SEO when embedding images in a guest post or other pages intended to get a link back to your site.
Image relevancy is important in websites. The Alt tag is probably the most important image optimization factor. Alt stands for alternate. The text in the alt tag is displayed in place of the image if the image can not be shown or is taking too long to load.