The PHP and Joomla version requirements for SocialMagick can be found in our Compatibility page.
Beyond that, you need to have installed and enabled either the imagick or gd extension in PHP. If you are not sure if this is the case, please check out our instructions. If you need to enable one of the two extensions, we strongly recommend the imagick extension which allows PHP to use the more powerful and flexible ImageMagick library for image manipulation. You can learn how to do so by reading our instructions on enabling imagick.
We strongly recommend using the imagick extension whenever you can. It renders colour much better, it is faster, and it supports SVG files.
The gd extension is older, it does not render colour as well (the colours look either washed out or with too much contrast compared to what you see on your browser and the image source file), it is slower, and it does NOT support SVG files at all.