The "Share design" option allows you to share a link to your design with others, via a link or by email. By clicking the link, anyone with access to the link can open your design in the PosterMyWall editor. Don't worry, they will open only a copy of your design (unless specified otherwise) and your original design will remain unchanged.
This option is useful if you'd like others to edit your design in the PosterMyWall editor. This can be used to collaborate with others in designing.
The Publish to Social Media option allows you to share the design, as it is, directly to social media. The image or video will be viewable as a social media post and if it's a video, it can be played. If the published video or image was purchased prior to publishing, it will not contain a watermark.
Get a quick rundown on publishing to social media via the editor by watching this video.