Typical use cases (scenarios) for AlwaysOn and availability groups include the following:
Need for High Availability nearing five-nines (99.999% available). This means that your database layer must be super resilient to failure and have nearly no data loss in the case of failure.
You have disaster recovery (DR) needs that need to replicate data to another site (perhaps on the other side of the country or planet), but you can tolerate a little bit of data loss (and data latency).
You have a performance ...