Taxiway

A taxiway is a surface in which aircraft can travel between the runway and the stands. In order to have planes travel to and from the runway and the stand, you'll need to place a path of taxiway nodes which aircraft can use to find their way.

Types of Taxiway foundations
There are three types of taxiway foundations. Concrete and Asphalt do not need to be repaired as often as grass. You can upgrade the taxiway at any time by simply placing it over of an existing taxiway foundation.

E.g lets say you have a grass foundation and you want to make it asphalt, select asphalt in the taxiway foundation menu and place it on top of the existing grass foundation.

Runway Entrances
Runway entrances are items placed along a runway for aircraft to enter/exit the runway. They come in grass, asphalt, and concrete. Asphalt and concrete entrances also have angled variants, which as of Alpha 33 serve no purpose but to be aesthetically pleasing. You can click on the entrance and choose, with a slider, whether that entrance can be used to enter, exit, or enter and exit the runway at that entrance. Aircraft will wait at the entrance before entering the runway.

Taxiway Nodes
Taxiway nodes are placed along a taxiway foundation to give a path for aircraft to take between the runways, gates, and any other places the aircraft must travel to along the ground. Nodes can be placed diagonally, vertically, and horizontally. Junctions will be created automatically when two sets of nodes cross each other. They can also be set to one way.