The (unconfirmed) story goes that Francisco Tárrega composed Lágrima in 1881,
while performing in London.
He was depressed and homesick, and he wrote a song describing his state.
Lagrima is a prelude that consists of two 8-bar sections (A, in E major & B in E minor), each of which is immediately repeated.
On reaching the last bar, after having repeated the B section, the D.C. al Fine sign comes into effect.
It means go back to the start and play again until you reach the Fine sign which signals the end of the piece.
So the sections are played as A A B B A.
For my ukulele rendition i had to traspose the piece in C, so the A section is in C Major, and B section in C minor.
Here a brief video of A and B sections sequentially played: