Is this a real rotary hammer or a drill with a hammer mode?

It is a real rotary hammer with a piston-driven hammer action and 1.2 joules of impact energy. That is at the low end for the class, so treat it as a light-duty masonry tool.

Will it drill into concrete?

Yes, in soft or light concrete and small-diameter holes. In hard or reinforced concrete it will be slow and may stall, where a corded SDS-Plus hammer would keep going.

Does it come with a battery and charger?

It is commonly sold as a bare tool. Check the listing carefully; if you are not already on the Greenworks 24V platform, you will need a battery and charger.

What bits does it take?

It uses SDS-Plus bits for hammer drilling. For plain drilling and driving in wood or metal you need the appropriate chuck or bit adapter.

Is it worth it over a corded hammer drill?

If you already own Greenworks 24V batteries and do occasional brick or block work, the cordless convenience makes sense. For regular concrete drilling, a corded SDS-Plus rotary hammer gives more power for the money.