Image compression is reducing the size of the graphics file without degrading the quality of the image. In terms of website, image compression helps in fully increasing the speed of your website and if your graphic is heavy in size like greater then 1 MB, it will take long time to load. See below, I am uploading two images one is compressed and another is uncompressed you will see the difference in its load time and quality.
|Original (61.5 Kb)||Compressed (28.7)|
There are so many online tools to reduce the size of image some of them are as follow.