What s the difference between Google Cloud Spanner and Cloud SQL

Question

I am new to the GCP stack and am overwhelmed by the variety of GCP solutions available for data storage:

https://cloud.google.com/products/storage

Despite the fact that Google Cloud Storage is not mentioned in the aforementioned article, I am aware that it exists and is used for data storage: https://cloud.google.com/spanner.

In my present opinion, there is no discernible difference between cloud spanner and cloud SQL (which uses Postgres as its database engine). Although I discovered that it has a little different syntax, it is unclear whether I should choose this technology over spring cloud SQL.

Would you kindly elaborate?