Konglish (Korean: 콩글리시) is the use of English words (or words derived from English words) in a Korean context. The words, having initially been taken from English language, are either actual English words in Korean context, or are made from a combination of Korean and English words. It is considered a sublanguage (linguistics).

Origins of Konglish
In South Korea, the term Konglish is used to refer a variety of English spoken with a Korean accent. Its pronunciation is closest to American English, influenced by American TV shows and movies, with some British English elements. This makes it the second Asian variety of English based on American English pronunciation after Philippine English. But there are still some differences:

Words ending with consonants, except b, d, g, and s, are appended with a schwa.
Final consonant clusters add a schwa at the end, while at the beginning of the word, a schwa is inserted between the consonants.
Voiced "th" (ð) like them is pronounced "d" and voiceless "th" (θ) like thrill is pronounced "s".
l and r are allophones in Korean. Final and initial r are sometimes pronounced as l. Speech is sometimes non-rhotic.
Unaccented vowels a, i, o, and u in final syllables before consonants, except, l and r, are pronounced in full vowels.
Fs are pronounced p or h, since there is no widely used f sound in Korean. There is a special pronounciation "ㆅ."
Vs are pronounced b, since there is no v sound in Korean.
Zs are pronounced j, since there is no z sound in Korean.
Rs are pronounced as alveolar flaps [ɾ]. Elements of Konglish
Another aspect of Konglish is the inclusion of English words in Korean sentences, or the use of Korean words in English sentences. This phenomenon can be commonly seen in the culture of second and third generation Korean-Americans. Here, the supplanted words are often loan words used to fill the gap of a limited Korean or English vocabulary. These borrowings may be seen as being used to compensate for a deficiency (or perceived deficiency) in either English or Korean.
This behavior, referred to as code-switching by linguists, may be an expression of the speaker's desire to be included in either the English or Korean speaking community even though this speaker lacks complete fluency in the respective language. In this case the use of a mixed Korean Immigrant Konglish can be seen as an attempt to gain entry into the social group even though there may be something of a lack of language ability.
Another possible rationale for the use of English words in Korean sentences or Korean words in English sentences may simply be that these linguistic borrowings help the speaker to better convey their meaning than if only one language were used. Because of cultural differences between American and Korean society, there may be no single corresponding word to concisely express an idea in the other language. It may, for example, be simpler to merely say something such as "I helped my father because of hyo(효)" than to say "I helped my father out because of a deep sense of traditional Confucian filial piety". This is especially true when both the speaker and listener are familiar with the borrowed term.
Finally, this form of Korean Immigrant Konglish may be used between fellow Korean Immigrants who wish to express their unique identity that is neither wholly of the adoptive country nor wholly Korean, but a complex fusion of both. This should not to be thought, however, that these speakers are trilingual speaking Korean, English, and this form of Konglish with equal fluency. Generally people who speak Konglish lack the ability to speak one of either of the languages of English or Korean fluently. It is, however, correct to assess that by speaking some from of Konglish (speaking neither English or Korean), these speakers are signaling their membership in this special Korean Immigrant subculture. In so doing, speakers of this type of Konglish act to exclude both Korean speakers who lack an understanding of English, and English speakers lacking the ability to comprehend Korean. In this way, Korean Immigrant Konglish has become the unique language of this cross cultural second and third generation immigrant group.

Korean Immigrant "Konglish"
It is also worthy of note that the term "Konglish" has taken on a second meaning among the English-speaking ex-patriate population of South Korea. It is used commonly to refer to misuse of English, typically on signs, menus, t-shirts and stationery, often with comical results.