I have gone through many articles and understood partially. Anyone Can you please generalise with this service and managed accounts?
Service Accounts are all the accounts you should use to have a best practice installation of any SharePoint Server. They are ...
... and typically lives in your Active Directory as Managed Service Accounts (not to be confused with SharePoint Managed Accounts). Typically (if we follow AutoSPInstaller default settings), the accounts in Bold are your SharePoint Managed Accounts
Now SharePoint can manage some of these accounts, by which we call them Managed Accounts (by SharePoint). SharePoint can update password to follow password rule settings to name one thing. You can see your managed accounts by running the PowerShell script
Which "Retrieves accounts registered in the configuration database."
Service Accounts accounts used within sharepoint to run the services, app pools, cache etc are called services accounts. These of domain accounts created within active directory. Like farm admin account. You can use any domain account in sharepoint but once it being used in sharepoint called service account.
Managed Account is a utility within sharepoint, which provide you functionality to manage services accounts easily.like if you want to change the password of a service account(I.e farm admin) then you can go to managed account section of central admin and edit the farm admin account, sharepoint automatically update the password across all servers. You can store multiple services accounts in managed account utility.