1) savepoints

Here is an asktom thread describing savepoints and potentials uses:

https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:496653103575

2) updating a view

If the view maps directly to a table, (or one of the tables in the definition), but that I mean, the row in the view has 1-to-1 with the row in the table based on its primary key definition, then you probably will be able to update the view (and the table will be updated).

More info here https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:548422757486

3) materialized views

As the name suggests, we take the SQL from a view, actually run it and store (materialize) the results. We might choose to do this when the SQL takes a long time to run, and lots of people want to run it. So it may be more efficient to run it once and store the results, and point people at that.

4) indexes

Oracle auto-creates indexes for you in *some* circumstances, to enforce a primary key or uniqueness constraints. You can create indexes for other reasons as well, but that's a very big topic. I'd suggest you take a read on the indexes section in the Concepts guide.