The Esri website has two flavors of user accounts: Esri and ArcGIS Online (AGOL) accounts. The main management site for these is accounts.esri.com.
Esri account
This account is also known as your MyEsri account, ArcGIS Online public account, or (formerly) Esri global login.
The Esri account is designed to be a individual, personal identity as an Esri user, not specifically identified with an organization, so it will travel with you through your GIS life. This login should be used to access your public (free) ArcGIS Online account, community.esri.com ("Geonet"), earlyadopter.esri.com, and other Esri sites. Esri site administrators from your organization log in to MyEsri and in turn add your Esri login identity to the organization (yes, MyEsri organizations, different from ArcGIS Online organizations!). The Esri site administrator than can grant you access to training, software downloads, and other items like User Conference passes. You can log in to MyEsri and then "connect" to any organization to which you have been added (if any) to access resources granted to you by your MyEsri organization's site administrators.
ArcGIS Online account
Also known as an AGOL organization account, AGOL organization login, or ArcGIS license portal login.
Users normally have one login per each AGOL org they belong to. AGOL usernames usually have an organization suffix to help admins identify their users, and keep the usernames unique across ArcGIS.com. For example: jwpowell_USGS, N.Darton_SDMines. The AGOL login is used to access and use your organization's AGOL (subscription) site org.maps.arcgis.com, and also to authenticate named user licenses (currently, only ArcGIS Pro) from the arcgis.com or <org_name>.maps.arcgis.com license portals (either works, using your AGOL org username and password). Single Sign-On can be enabled by the AGOL administrator, if this is the case, AGOL users can login using their organization's credentials, and (depending on how the identity provider is configured) their username may look something like: email@my.org_orgmaps or user.name_orgmaps, where "orgmaps" is the AGOL organization name.
Esri Access
ArcGIS Online administrators have the ability to enable or disable Esri Access for each user. If Esri Access is enabled for that user their AGOL account can access MyEsri and the Training site with the same login credentials. Though this is convenient for your MyEsri and ArcGIS Online administrators, if you ever are removed from your AGOL organization (new job, site re-configure etc) all your MyEsri information (contact info, training record, content) will not be available without asking Esri Customer Service to move it to a new (public) MyEsri account. (Note, Esri customer service can do this easily, if you ask.) Even if you have Esri Access to access training, another advantage maintaining a MyEsri account is you can participate GeoNet (community.esri.com) site using your MyEsri account without being associated with your AGOL org, making it clear that you speak for yourself and not your organization!
"User is not enabled for Esri Access"
If you get an error User is not enabled for Esri Access when trying to access your Esri login (for example to access training) switch accounts to the MyEsri account under which you have training access (the AGOL site has an option to connect your locations for easy switching as needed). If all else fails, restart your web browser to log you out of everything, visit my.esri.com and login with your MyEsri account. (If you don' t have a MyEsri account, create one.)
Additional Reading
https://community.esri.com/community/education/blog/2018/10/09/what-is-the-difference-between-my-esr... https://accounts.esri.com/en/commonquestions
Esri Accounts FAQ
ArcGIS Online Help / Create Account
ArcGIS Online Help / Account Troubleshoot
ArcGIS Online Help / Administration / Manage Members
https://community.esri.com/groups/esri-training/blog/2017/04/20/tips-for-e-learning-administration?s...
Resolving GeoNet Login Issues
