Here is the information from chapter Registering Tasks in Sitecore Database from a book Professional Sitecore Development written by John West:
In addition to agents defined in the Web.config file, you can create task definition items in a Sitecore database. Ironically, Sitecore uses the DatabaseAgent and TaskDatabaseAgent agents defined in the Web.config file to invoke tasks defined in a Sitecore database. The difference between these two agents is that you must specify the database using the first element of the DatabaseAgent /configuration/sitecore/scheduling/agent element in the Web.config file, whereas the TaskDatabaseAgent determines the database from the first element within the /configuration/sitecore/TaskDatabase element in the Web.config file. The default Sitecore configuration invokes tasks defined in the Master and Core databases.
I understood the out-of-the-box way of using DatabaseAgent (by creating .NET logic, command item and schedule item in content editor) from this link: https://community.sitecore.net/technical_blogs/b/sitecorejohn_blog/posts/repost-all-about-sitecore-scheduling-agents-and-tasks
Could someone please explain to me how to use the TaskDatabaseAgent out-of-the-box way (e.g. which out-of-the-box action that helps to insert record(s) into Tasks table in Core DB)?