What is meant by permission marketing?

What is meant by permission marketing?  Do you think it is an important concept to email marketers?

Permission marketing

Permission marketing is getting permission to market to consumers. When a business wants to send emails it is essential to have their permission because the consumer wont disregard the email because they filled out information to get the information sent from that company. A lot of people are flooded everyday with marketing that doesn’t pertain to them so permission marketing also limits to what people see, and they only see marketing on products they are excited to learn about, and not useless information.