For those new to port, here's what I (think I) know about it, as a regular port-drinker and buyer:
There are really four (common) types of port:
Ruby
Tawny
Vintage
Late-bottled vintage
Each of these types can be made with red grapes or white grapes; white port is swill (cue flame war), so the rest of this post is exclusively about red port.
All port is fortified with a neutral alcohol before formentation is complete. That leaves much more sugar unfermented (thus the sweetness) and increases the alcohol content significantly (usually to 20%). Ports are then stored, either in barrels or bottles, for at least a few years, before being (bottled if necessary and) sold.
Ruby ports are the simplest, made almost always from a blend of grapes (possibly from different years), with the goal of having a consistent flavor year after year. Ruby ports are aged in bottles (or non-wood casks), so they tend to be sweeter and syrupier than other ports. Ruby ports can be drunk immediately, or stored for a few years.
Tawny ports are the other end of the spectrum - aged in wooden casks for many years (10-40 is common), so they take on similar notes to whiskeys, and are usually not syrupy at all. Tawnys are also usually made from a blend of grapes (possibly from different years). Tawny ports can be drunk immediately, or stored for a few years.
Most people prefer rubys or tawnys, but not usually both.
Vintage ports are more like regular wine; they come from a single grape and a single year (thus "vintage"), and are stored in wooden casks for a maximum of two (or three?) years. Usually vintage ports are only "declared" and bottled when the grower/shipper expects that year to be a great one (~3 times a decade), so it is a bit of a gamble on the grower's part, but usually a good thing for the consumer. They are more like ruby ports than tawny.
Late bottled vintage (LBV) ports are like vintage ports, but they are stored in the casks for an extra year or two. They take on more whiskey-like character, but still have a little bit of the syrupy flavor associated with ruby ports.
Choosing a vintage (or LBV) port is a lot like choosing any red wine - what you get depends enormously on the region, the winery, the weather/year, the choices made by the winery, and the age of the wine. Vintage port is an entire wine class of its own, so it is hard to give advice about a particular year/label without knowing the details of the weather in that region that year, and without tasting it, and without putting some trust in the winery 
With that said, vintage port is almost always a great port.
P.S. - some vintage ports can (and should) be drunk immediately; some should be aged in the bottles for decades. It's hard to know without advice from the winery and/or an expert in the region and weather for that year. (Which I'm not.)
