Here you can find some definitions to help you better understand the "Maemo linguo" as it comes with its own versioning scheme and specific projects.

About Maemo

Maemo is the core software stack that runs on mobile devices like Nokia's N810 or N900, it is based on Debian.
Maemo's garage is where the projects for Maemo can be hosted, somewhat compareable to Sourceforge.
Maemo versions:
- 4.0, codenamed Chinook
- 4.1, codenamed Diablo, unofficial Qt support
- 5.0, codenamed Fremantle, first one to have official Qt support
- X.X, codenamed Harmattan, is a Maemo release which implements the Meego API, it was officially released as Meego 1.2 Harmattan.
Nokia devices running the Maemo stack:
- N770, first Maemo based internet tablet, runs Maemo 2.2 (aka OS2006)
- N800, internet tablet running Maemo 4.0
- N810, internet tablet running Maemo 4.1
- N900, first Maemo based phone, runs Maemo5 (5.0 initially, upgraded later to 5.0 PR1.1)
- N950, developer only not for sale device running Harmattan
- N9, first Maemo/Meego end user device running the same software as the N950

Build environments

Scratchbox is a cross-compiling environment used by the Maemo community for development and packaging, it tries to emulate the whole platform at build time extensively using qemu;
MADDE is a newer cross-compiling environment, simpler and more streamlined than scratchbox, it behaves more like a classical cross-compilation environment and doesn't rely on qemu during builds.

Busybox is a single binary that allows you to run commands like ls, cat and bunzip2;
Hildon is an application; framework and desktop shell for Maemo, compare it to the role that Plasma plays in KDE 4;
Mer is a Maemo community driven project which focuses mainly on porting Fremantle to the N8x0 devices.