"A Haunted House" is a ghost story with a nice twist - not a horror story though.
"A Society" is an almost science-fictional story of some women who form a society to observe men in order to determine, in effect, whether the species is worth continuing. The end is disappointing, but I suspect nothing more radical could have been thought of in 1921.
"Monday or Tuesday" is a weird little stream of consciousness vignette.
"An Unwritten Novel" is a set of speculations about a woman Woolf (presumably) sees in a railway carriage. It shows (I presume) her creative process at work.
"The String Quartet" did not make much of an impression on me at all.
"Blue and Green" is another stream of consciousness vignette, or rather two vignettes ("Blue" and "Green").
"Kew Gardens" observes a small spot in the titular park, and the various events that take place in that spot over the course of an afternoon, including the attempts of a snail to get past a leaf.
"The Mark on the Wall" is a near-horror story remniscent of Charlotte Perkins Gilman's "The Yellow Wallpaper." A woman obsesses over a spot on a wall until it turns out to be a snail that has somehow gotten into the house.
As a whole, the collection shows that Woolf's range this early in her career was huge.