Transparent Page Sharing is the ability for virtual machines to share identical memory pages. This allows hosts to most efficiently use memory, particularly when those hosts have many almost identical VMs running on them. The net benefit is better memory usage when it is actually leveraged (which isn’t always), potentially leading to greater consolidation ratios. TPS has been around almost as long as VMware.
As the blog post below indicates, VMware is making a change to the default settings for TPS in proactive response to theoretical security research. I encourage you to click-through to learn more.