For a long time now, Linden Lab has offered a free Linden Home to Premium members of Second Life. These were always intended to be "starter homes" and as such, they have a number of limitations. The most obvious is, they're small. They are on 512 square meter parcels, and until recently only allowed 117 prims (the recent prim limit increase to Mainland regions has raised that to 175.)
Besides being small, you can't get rid of the Linden Home and put a house of your choosing on the parcel, or place a skybox above it.
Linden Lab is attempting to address these limitations with a new offering in the Horizons regions. The Horizons Experience is a quest-type game against the clock, featuring a number of challenges. But besides the game, the new Horizons regions offer residential parcels. These are 1024 square meters in size.
You can rez your choice of several pre-installed Horizons-themed houses (which don't count against your 350 prim allowance, similar to a Linden Home), or you can place your own structure.
Horizons parcels are NOT offered as a free Premium benefit. You can, however, use your 512 sq. m. land allowance and apply it to your Horizons parcel. That means that you will only pay tier on the remaining 512 sq. m., or $5.00 USD per month (in addition to your Premium membership fee.)
Horizons parcels are currently being sold on the Land Auctions page. After they've been auctioned off, the only way to get one will be to buy it from another resident, or find one that has been Abandoned by its former owner and purchase it from "Governor Linden."
Surprisingly, the Horizons regions are rated Adult. This is a departure from the Linden Homes, which are on Moderate regions. I would never have expected LL to associate themselves so closely with Adult activities...heck, just a few years ago they scraped up all the Adult stuff on the Mainland and exiled it to a whole separate continent, Zindra.
For lots more about the new Horizons land parcels, see this Wiki entry: http://wiki.secondlife.com/wiki/Horizons_Parcel_Ownership
I'm sure these will be of interest to many people, especially those fairly new to SL. But, as a landlady, I'm feeling quite grumpy about them. Once again, Linden Lab is setting itself up in direct competition with the Residents. Phooey.