Geological feature - what is it?
1) I would call the formation a sea stack.  Effectively you have a band of rock which is either more resistant to the forces of erosion and weathering from the sea, or is located on top of a more resistant strata.  The more eroded portion is just that, a more eroded portion, and by its absence tend to identify the rest as a sea stack.
2) The matrix, the rock with the fossils, looks like a limey shale, or a limestone with a lot of shale or clay in it.  It appears to have a component of lime or CaCO3 in it.  This could be confirmed by placing a small amount of dilute HCL or Muriatic Acid on the rock and seeing if it fizzes.
3) There are definitely crinoid stem sections in this rock, as mentioned by JulPal.  If you look carefully at this rock you will likely find a number of other fossils.

To get a tighter description you will have to give more information about the rocks

Treatment of this rock with a dilute acid bath might show a number of fossils.  See the article here https://museum.wales/articles/2011-06-07/Fossils-in-stone-acid-preparation-of-fossils/