Let's play with consonants.
The first thing to realize about Korean is that certain consonants are closer to others than in English. Wow. What a terrible sentence. Patience, please.
I think, if you were to ask most people what letter "B" is most similar to, they would respond with "D". How about "G"? I think most people would say "J", because of the way English is formed.
In the Korean language, there are a few sounds that are something of a "sliding scale" phonetically, and they share written letters. For instance, make the "G" sound (guh) and then make a "K" sound (kuh) and notice how similar they are when being formed. The same goes for "B" and "P", "G" and "K", "J" and "ch". That's about all there is difficulty-wise for Korean consonants.
ㅁ ㄴ ㅎ ㄹ ㅇ
These letters are M, N, H, L, and ng (as in "well-huNG"). They are exactly the same as English.
ㅂ ㅅ ㅈ ㄷ ㄱ
These letters are "sliding scale" and they are B, S, J, D, and G
ㅃ and ㅍ, ㅆ, ㅊ and ㅉ, ㄸ and ㅌ, ㅋ and ㄲ
If you say them a bit "harder" they sound like this. P, ss, ch, T and K. This is the kind've the dumbed-down version of how these sounds work, but that's the gist of it.