it is hard to explain it in Englis, but i try.
ㄱ ㄴ ㄷ ㄹ ㅁ ㅂ ㅅ ㅇ ㅈ ㅊ ㅋ ㅌ ㅍ ㅎ ㅃ ㅉ ㄸ ㄲ ㅆ- they are consonats
ㅏ ㅑ ㅓ ㅕ ㅗ ㅛ ㅜ ㅠ ㅡ ㅣ- these are vowels.
usually we need one velow and one consonant to make one syllable.
for example. 가, 갸, 거, 겨, 고, 교, 구, 규, 그, 기 - each is one syllable.
However, two consonants and one vowel also can be one syllable.
for examlpe, 각, 간, 갇, 갈, 감, 갑, 갓, 강, 갖, 갗, 같, 갚, 갛, - each is also one syllable.
In addition, one consonant and two vowel can also be one syllable.
For example, 개(ㄱ + ㅏ +ㅣ), 걔(ㄱ + ㅑ + ㅣ) 게(ㄱ + ㅓ +ㅣ) 계(ㄱ + ㅕ+ㅣ)
과(ㄱ+ ㅗ+ㅏ) 괴(ㄱ+ㅗ+ㅣ) 귀(ㄱ+ㅜ+ㅣ) 궈(ㄱ+ㅜ+ㅓ) 궤(ㄱ+ㅜ+ㅔ)
two consotants and two vowel also make one syllable.
For example, 곽(ㄱ+ㅗ+ㅏ+ㄱ) 관(ㄱ+ㅗ+ㅏ+ㄴ) 괌(ㄱ+ ㅗ+ㅏ+ㅁ) 괄(ㄱ+ㅗ+ㅏ+ㄹ)
so~~ combining syllables will be one words.
for example, 안녕하세요.(It means Hello in Korean) - this word is a five-syllable word.