Active vs Inactive Contacts

Hi SK-
If you have an active flag on your SFDC records, it all depends on how your team has used it in the CRM system.  In our case, contacts were marked as Inactive if they a) left the company that they were listed under, b) they died (literally), or c) if there was no interaction by marketing or sales to that person within two years.  Then, inside MKTO, we'd use the filter of Active TRUE  to include them in any smart campaign to increase our deliverability chances in deployments.

Hope this helps!

Thanks Brigid. 
My question is - Is there any concept of Active/Inactive contacts in Marketo. If yes, how Marketo defines Active and Inactive accounts.

Thanks.