ive played all the fallout games and have gotten all endings none explain this

There is more than one GECK.

Yeah there's a handful of GECKs...

Many Vaults are issued G.E.C.K.'s, so it isn't weird there's one in Vault 87. What is weird is how the G.E.C.K. changed from a case with a small nuclear reactor, fertilizer, seeds and manuals on how to survive the wasteland and live off the land turned into some kind of powerful, terraforming device.

According to Vault Tek's marketing matierial and the vault dwellers survival guide (VDSG), each vault is equipped with 2 GECKs.

In Fallout 2, it was revealed that V13 had 3, whereas Vault City (8) only had 1 due to a shipping stuffup. It is presumed that V15 also had 2 Gecks; although there isn't anything to suggest that Necropolis had any (beyond the VDSG). Each GECK has one use only (although some items such as the library of Congress archive and the handy flashlight are clearly reusable, the stuff that cities are built of apparently aren't).

In Fallout 3, it was established that not all Vaults had GECKs afterall, these were secretly only issued to selected vaults. The V87 GECK is not the V13 GECK, nor the V8 Geck. It is also speculated by fans that there are 2 varieties of GECK, the world-changing Fo3 style, and "discount" variety style indicated by the Fallout Bibles (where its basically a manual and a bunch of seeds), but there doesn't appear to be any canon to confirm this theory.

It is as yet unknown if there are unused GECKs still out there.

Agent- with the Vault Tec marketing material I think that only applies ot the 13 or so Vaults that were built according to marketing ads (Vault 8 is an exception due to the shipping error mentioned earlier.

Exactly no point giving GECKS to every single vault when you expect most of them to fail horribly.

Especially if they're as powerful as the Fo3 GECKs.

The F3 GECk is cooler IMO... It make Braun seem more like a genius and it makes land that has a GECK clearly different from lands that don't.

There is more then one G.E.C.K out there :facepalm:

The GECK from Vault 13 was used to make New Arroyo.

Vault City was made using a GECK

and on the Enclave oil Rig is a second GECK

As other memebers pointed out there was to be two gecks for each vault. If they got them or not is another matter.

I like the FO3 GECKs better, but I just wish some explanation could have been given as to what its technology contains and how it works.