What is an email sequence?
An email sequence is a series of emails automatically sent to your customers. They are spread out over time. So the first email could be sent one hour after subscribing. The second email one day later, the third one three days, and so on. An sequence can contain 10 different emails.
In Seos they are triggered with an automation. So if something happens (a new customer, a charge of $500 or based on a segment), then add them to the sequence.
As every email sent from Seos has an unsubscribe link, your customer can unsubscribe at any time, thus not receiving the following emails within the sequence.