Obama is noted with 199 superdeledates and Clinton with 238
when and how did they “win” these delegates ?
Those are the superdelegates who have publicly stated who they intend to vote for at the convention.
Correct. Note though that they can, and some have, change their mind.
Those delegates are not won by vote; they’re Democratic politicians (for the most part) who have what’s called “Superdelegate” status-- they can cast their vote for whomever they wish.
Are there any official rules about how they decide to vote for “whomever they wish,” like not accepting bribes or concessions from the candidates?
The superdelegates are holders of political office or party officials. They aren’t going to do anything that smells too bad, to avoid jeopardizing their careers. Here’s the seated superdelegate list:
Note that it is a collection of DNC officials, congresscritters, senators and state governors.
This makes more sense if you remember the historical perspective. Binding primaries were not always the preferred method for parties to choose their candidates. Primaries of any type were something that came about as a progressive movement reform in the early part of the 20th century. After 1968, when the binding primary really became the preferred method, the party committees were hesistant to turn the process completely over to a popular vote, and continued to have some unpledged delegates that operated as convention delegates had in the past.