This is the part of the agreement where Automattic asks a few things of you. First, the company wants your assurances that none of the content on your site infringes the intellectual property rights of others. In other words, you're representing (or "promising") that any content you post on your WordPress site either belongs to you or was posted with the permission of the owner.
For example, posting the steamiest chapters from Fifty Shades of Grey without the publisher's consent would likely violate this representation. See the “Indemnification," "Copyright Infringement," and “Termination” sections to learn about what could happen if you violate this part of the agreement.