Achievement: Threaten two loosely connected strings at once
By blocking one liberty of the D16 string, White creates a miai situation for Black. Both D16 string and F14 have just two liberties now. If Black tries to connect up the D16 string, White gets to take the F14 string. Likewise if Black tries to connect to his F14 string. B-E15 makes a more complicated fight, but I think W can get a reasonable outcome with it.