Can be used to set reminders on your phone or desktop. also can be used to create to-do lists and notes.
Much like Word, google doc has similar features, but a different format. As it is a online platform, you are able to sync it with multiple devices . In my opinion the best feature is the ability to convert the doc easily into a PDF or other formats. Another cool feature is being able to have multiple people edit the doc at the same time.
Just like google docs, google slides is very similar to PowerPoint, not to mention that you are able to convert the slide into a PowerPoint once you are done.
If you used all the storage in your onedrive account, you can get 15 GB of storage with google drive. Since it is a part if the google ecosystem, your google docs and slides will be automatically saved into your drive.