Is a pickled cucumber just a pickle?
Yes.  Basically, it is pickled in a brine, vinegar, or other solution and left to ferment.
How long does that process take?
I'm really not sure about that but they are only known as pickles in the US and Canada.  Other countries call them gherkins.  
What else do you know about them?
Sometimes cucumbers are brined which is a fermentation process that makes them grow sour.
Can they get too sour?
brine which makes them grow sour. The brine concentration can vary between 20 to more than 40 grams of salt per litre of water ( or ). There is no vinegar used in the brine of naturally fermented pickled cucumbers.
The fermentation process is dependent on the Lactobacillus bacteria that naturally occur on the skin of a growing cucumber. These may be removed during commercial harvesting and packing processes. Bacteria cultures can be reintroduced to the vegetables by adding already fermented foods such as yogurt or other fermented milk products, pieces of sourdough
Pickled cucumber
A pickled cucumber (commonly known as a pickle in the United States and Canada and a gherkin in Britain, Ireland, Australia, South Africa and New Zealand) is a cucumber that has been pickled in a brine, vinegar, or other solution and left to ferment for a period of time, by either immersing the cucumbers in an acidic solution or through souring by lacto-fermentation. Pickled cucumbers are often part of mixed pickles.
Historical origins.
It is often claimed that pickled cucumbers were first