Once your home is listed in the multiple listing service (MLS), your agent will begin marketing your home to ensure it gets in front of as many potential homebuyers as possible. Since over 95% of consumers search online to find their next home, according to the National Association of Realtors Profile of Home Buyers and Sellers, your agent will likely 'syndicate' your listing to all of the major real estate websites. Syndication is the process of publishing your listing to multiple sites at the same time.
Using the property details, the written description, and all of the digital media they've uploaded (photography, video, floorplans, and 3D tours,) the MLS will forward that along so that it displays on sites like Realtor.com, Zillow, Trulia, brokerage websites, and your agent's own personal site. The process is automated, so when your agent edits the information, like changing the description or adding an open house, the change will publish to all of the rest of the websites. The time that it takes for the information to display on the sites after a change is made varies by website and can be as quick as a few minutes or as long as 24 hours or more.
Brokerages typically accomplish this for their listings by utilizing IDX, short for internet data exchange. Brokers grant permission to other brokerages to display their listings online, with the attribution of their firm as the source of the listing. While some third-party portals, like Zillow, allow homeowners to claim their home listing and edit information, it's best to let your agent make edits while the home is actively listed so that a duplicate listing isn't created.
Your agent can give you additional details of where your home's listing will be shared online.