When tables share more than a few of the same fields, it is quite often beneficial to extend other tables. Indeed, there are a few tables in ServiceNow which are meant only to be extended, and never to have records created on themselves. The Task [task] table is a prime example that we already have some familiarity with. We'll go into some detail on the task table in particular in a later chapter, but we'll use it as an example here just to touch on the topic of inheritance.
When one table extends another table, the child table inherits any fields on the parent table. All inherited fields are on the child table, and do not need to be dot-walked to, to be accessed. This has innumerable benefits, such as being able to search for a record on a base table, and discover records in all child-tables. Again, using the task table as an example, you might want to see all work assigned to you. The task table is generally where work records are stored (incident tickets, requests...