They are literally inside but....
Let's have some examples from dictionary. It's really hard to explain but they are slightly different.
eg. 집안(O) 집속(X)
I'll start with 안
안
①『내부』 the interior; the inside. ②『미만』 inside of; within; less [not more] than; during (┅중에). ③『뒷면』 the back; the wrong side; the reverse side; the other side; the under surface(아래쪽); the inside (내면).
┈┈• 집[차]안에 in the house [a car] ①
┈┈• 안에(서) within; inside; indoors ①
┈┈• 안의 사정 the internal affairs ①
┈┈• 안으로부터 from within; from the inside ①
┈┈• 안으로 모시다 let [show] 「a person」 in ①
┈┈• 공을 상자 안에 넣다 put a ball into the box ①
┈┈• 안으로 들어가다 go [come, get, step, walk] in
┈┈• 안에서 놀다 play indoors ①
┈┈• 집 안에서 나오다 come from within the house ①
┈┈• 집안에 들어박혀 있다 stay indoors; be confined to one’s house; stick 「at home [in the house] ①
┈┈• 집안은 모든 것이 뒤죽박죽이었다 There was a great hubbub inside the house. or All was confusion within the house. ①
┈┈• 문이 안에서 열렸다 The door opened from within. ①
┈┈• 그의 장래는 내 손안에 있다 I have his future in my hands. ①
┈┈• 일주일 안에 within [in less than, inside of 「미」] a week ②
┈┈• 그 날 안으로 in the course of the day ②
┈┈• 기한 안에 within the time limit ②
┈┈• 한 시간 안에 회답하겠습니다 I will give you my answer in an hour. ②
┈┈• 천의 안쪽 the wrong side of the cloth ③
┈┈• 안을 뒤집다 turn inside out. ③