HubSpot Sequences are for Sales activities (Conversation Templates and Tasks), whereas HubSpot Workflows belong more to the Marketing team.
Workflows allow you to control customer data and to make sure customers get the right content at the right time. You can use Workflows to automate important activities across your entire HubSpot portal, from Marketing to Service.
Sequences are strictly for Sales Professional users - and strictly for the 1:1 management of a sales rep's leads and repeat customers.
Watch the video to learn more and to see HubSpot Workflows possibilities.