Hangul ᄀ = G/K and ᄁ = kk

This letter (giyeok ) can be pronounced like a G or a K depending on where it is in a syllable. It can also look different, for example it can look like ᄀ or ᄀᅠdepending on where it is in a syllable. If it comes on the side it will be curved and if it is on the top or the bottom of a syllable it will be in its original form. Examples:
기 (gi), 길 (gil), 김 (gim)

Study words that start with ᄀ on TinyCards – a Duolingo site.

ᄁ= kk

The second letter of the Korean alphabet is the letter ᄁ (ssanggiyeok ). It is a doubled giyeok ᄀ . It is pronounced with a harder kk sound thanᄀ.

See KoreanWikiProject for example syllables withᄁ.