Lens Naming Conventions
The first thing you might notice is that everybody seems to have a different way of naming lenses. The obvious parts - the focal length and aperture are pretty straightforward but even they differ in how they're expressed. In an effort to explain this and either fix or prevent bad habits (of which I'm guilty as well) here's a sort of "Rosetta stone of lenses."
Consider these sample lens names from various manufacturers:
Canon EF 50mm f/1.2L USM
Voigtländer 50mm f/2.5 Color Skopar
Zeiss Planar T* 2/50 ZM
Leica Summilux 50mm f/1,4 ASPH
Zeiss and Leica are German companies. Thus they tend to use a comma (,) rather than a period (.) when expressing values such as aperture. For example, f/1,4 rather than f/1.4. You could really use either convention. Leica used to use the comma more, but most new lenses use periods - unlike Zeiss which still uses commas. Voigtländer used to be a German company but the rights to the brand name were bought by Cosina, a Japanese company. The lenses, boxes and documentation are printed with periods but the (German) website uses commas (as is the norm there).
Zeiss and Leica generally use only the whole part of the aperture where possible (e.g. f/4) rather than specifying the decimal part on all lenses (e.g. f/4.0) - Voigtländer mixes both randomly.
It's worth pointing out that Voigtländer lenses are just that - not "Cosina/Voigtländer" which is often abbreviated as "CV" on forums. For the same reason you don't say "Cosina/Zeiss" when referring to ZM lenses (they're assembled in the same factory).
Further confusion arises from the order in which manufacturers list specifics of their lenses. Zeiss likes to abbreviate these, such as "1,5/50" whereas Leica and Voigtländer stick to a more conventional format of "50mm f/2." Zeiss and Leica state the lens name/design/family first, then these specifics - whereas Voigtländer does the opposite.
The most confusing aspect is likely the various features found on a specific lens, and each manufacturer has a different way of noting them. Voigtländer doesn't usually list them as part of the official name, though it's printed on the lenses and in the documentation. Zeiss doesn't list anything as they don't have aspherical or apochromatic lenses, but they do list their standard multicoating, "T*" on every lens... Leica is perhaps the worst offender, putting these features either in front of the lens family name or tacked onto the end of the name.
Finally, we come to the actual names of lenses. Leica follows a convention of naming lenses by family, according to their speed (e.g. Summilux = f/1.4 lenses). Zeiss uses lens designs (e.g. Biogon) and Voigtländer falls somewhere in between (e.g. Heliar vs. Nokton).
Here are common abbreviations as seen in lens names from various manufacturers:
ASPH - Aspherical (Leica uses both, though Aspherical is typically found on older lenses, ASPH on newer)
APO - Apochromatic
FLE - Abbreviation for "Floating Lens Elements" - unofficially used to distinguish between Summilux 35mm versions
-M - Used by Leica to denote a newer, M mount lens generally
C - Used by Zeiss to denote a "compact" or "classic" lens formula or Voigtländer to denote "Classic"
P - Used by Voigtländer to denote a "Pancake" lens
T* - Used by Zeiss to denote their standard multicoating
ZM - Used by Zeiss to denote the lens mount
LTM - An abbreviation for "Leica Thread Mount"