Hi JeniferZOrdonez , great question! We recognize the licensing is a bit tricky to figure out at the moment - so thanks for bearing with us. Planner Plan 1 is the equivalent of / was formerly known as Project Plan 1, so it enables you to access the premium functionality listed under "P1" here: https://learn.microsoft.com/en-us/office365/servicedescriptions/project-online-service-description/project-web-service-description. You can use this functionality in both Project for the web and premium plans in Planner Teams, and in the future this means you can also use premium functionality in the new Planner web. As for E5 licenses - the comprehensive list of what is available is listed under "Office 365 licenses" for the same link above. 

You can also compare E5 and P1 functionality with this link here: https://www.microsoft.com/en-us/microsoft-365/planner/microsoft-planner-plans-and-pricing. I hope this helps and do let us know if you have followup questions!