Translation:Bread is delicious.
There is a plural marker in Korean, -들, mostly used with living things.
It's also doesn't seem to be as "essential" as it is in English. Whereas saying "dog" in English implies a single dog (since it's a count noun without a plural marker like -s), 개 can mean either one or many dogs, and you would only worry about the plural marker if you want to emphasize that you're talking about several dogs.
은/는 was used to describe one specific thing and not a whole category.
It can be used that way, but that usage requires the context of a greater conversation. There is no definite and indefinite article counterpart in Korean. As such translations will vary from sentence to sentence. The bottom line is that 은/는 is the topic marker -- it marks the topic of the sentence, what the sentence is about.
"빵은" does not directly mean "a specific bread" or "a whole category of bread". The marker just indicates that the sentence is about 빵. It is within the context of a conversation that the topic marker can be used to add connotative meaning. For example:
A: 빵이 먹어보십시오. ("Try the bread.")
B: 빵은 맛있습니다! ("The bread is delicious!")
Note that 은 is used here to continue the conversation about the bread offered. The translation defaults to the specific bread. However, in the context of a different conversation, it can be used to add contrast between the single and the many:
A: 빵 삼개이 먹어보십시오. ("Try the three breads.")
B: 이 빵이 맛없습니다. ("This bread is not tasty.)
B: 그 빵이 맛없습니다. ("That bread is not good.")
B: 저 빵은 맛있습니다! ("That bread over there is delicious!")
Here, after trying the first two breads, B is making a contrast and saying that the third bread is delicious unlike the first two. He is emphasizing this contrast with 은.
Its called "denasalization". When ㅁ (and ㄴ) are the first sound of a word, sometimes the speaker doesn't let air to resonate in the nose causing ㅁ to sound like the English /b/ and ㄴ to sound like the English /d/. You can simulate this by pinching your nose and pronouncing ㅁ and ㄴ.