I find this super confusing, as well. Can anyone enlighten us?
I believe picture 1 (the film frames icon) indicates standard tweened frame blending (combined frames using dissolved opacity)
picture 2 (forward arrow icon) indicates pixel motion frame blending
picture 3 means no frame blending enabled
picture 4 (curvy line) indicates bicubic sampling for layer quality. This is a newer feature added in 2014 which greatly improves the quality of scaling/rotating a layer. I always enable this for any scaled or rotated footage.
Adam is correct. This is also explained in the help files, though it seems the page hasn't been updated to include all info:
Thanks, guys! I knew what they meant back when they were still the solid slash and the dotted slash, but Adobe changed the icons with CC2014 (I think it was CC2014?); at the time, I actually went searching for an explanation of the icons online,but couldn't find anything.
Thank you very much guys and Adam!!