Today I will explain the difference between "campaign" and "sequence"
Campaign: is a standard email you can send to your entire list of subscribers at once.
Once you create campaign, you have to select the "list" of subscribers you want to send the campaign to and SCHEDULE IT to be sent immediately or later.
Sequence: is an email used basically in your automation. It's designed to be sent to only one subscriber a time and not to an entire list of subscribers.
When you create "sequence" :
==> You DON'T NEED TO ADD LIST, because it's simply designed to work inside the automation.
==> You DON'T NEED TO SCHEDULE IT, because it will be sent for only one subscriber a time following the rule you added in your automation workflow.
Note: In automation workflow a sequence is considered like a single email with one content, and not like a series of emails.