To give (especially public) notice of (something); to announce publicly.
"The town square was filled with loudspeakers advertising the upcoming festival to everyone passing by."
In plain English: To advertise means to tell people about something you are selling or offering so they will want it.
"The company decided to advertise their new product on television."
Usage: To advertise something means to promote it publicly through media or signs in order to attract attention or sales. Use this verb when you are actively trying to get people interested in a product, service, or event rather than simply stating facts.
The word "advertise" comes from Anglo-Norman and Middle French roots meaning "to inform" or "to warn." It entered English through the Middle English form advertisen, eventually evolving into its modern spelling with a slight influence from the related noun advertisement.