DMCA or digital millennium copyright act is United States copyright law which prevents digital copyrights of the owners.
Well, DMCA.COM is actually a company which helps you to prevent content theft and piracy of your data.
In this digital age, it is very easy to copy your hard-work and paste it to some other website. DMCA.COM protects your legal data from the digital robbers by giving access to you to some tools and software.
You can use DMCA for finding if someone is copying your content, monitoring your content security, takedown theft content from other's website.
They are working with several governments and law firms to do this. They also provide various DIY tools and a website protection badge to deter the thieves to steal content from your site.