Purpose of Default Databases of Master Databases
1) Master Database :- It is Compulsory .If we delete this database then Sql Server Will not Start. It contain all entries like which database is stored at which location, login account info, link server info, instance info etc.
2) Model Database :- It is Common Templates for all databases. Database of size if not mentioned , then all such as properties or setting are stored in model Database and By Default these are setting are used by Database(Like Size of Transaction log File etc).
3) MSDB Database :- It is used for Scheduling.
4) Tempdb Database :- Used for temporary storage.Once the Service of SQL is stopped or Reset then all data in Tempdb Database Destroy or deleted.
5) Resource Database :- All System objects are stored in resource database physically.Logically these are present in all databases and these can be accessed by sys.schema