not sure where it stands for, but clearly around teh Resourch T... Package, it's the standard resourch any rpg maker come with.
to allow you to create teh game.
you can use your own graphic or mix or edit the RTP to a new unique tile while its stays RTP.
for example, you have a stairs that goes UP (this is basicly your base sprite or base tile)
make a copy and than rotate to the left or right (CW/CCW) than take each stairs and move 2-4 pixels down or up, depends
which diagonally you go, you can flip that horizontal to get the other side.
as for the railing, you can use a bit of a fence and take line by line and move 1 pixel down.
as for horizontal or bridge parts, it works a slightly different, but wood mostly works perfectly, with stone, not entirly sure
how to do that.
there are more ways how to achieve the desire effects.