It is a serverless object storage service
Billed based on the storage used and data downloaded

Files are called objects
Folders are called Buckets

Unlimited storage (theoretically) no minimum object size requirement
Low latency (Tens of milliseconds)
High durability (Nine 9s annual durability)
Supports Geo-redundant storage of data

Storage Classes

Standard Storage
Frequently accessed files
Has the highest cost

Nearline Storage
Files accessed once a month or less
Cheaper than standard storage
Data has to be stored for 30 days minimum

Coldline Storage
Higher access cost than nearline but lower at-rest cost
Data has to be stored for 90 days minimum

Archive Storage
Intended for data that will be accessed rarely
Very slow retrieval times (Data is stored offline)
Cheapest tier (No SLA present)
Data has to be store for 365 days minimum

NOTE

If the data is deleted before the minimum storage duration we will be charged for premature deletion