Terrain

Terrain is impactful on your movement and ability to interact with the world. Two ways to that terrain can make this impact is in dealing with elevated terrain and difficult terrain.

Elevated Terrain

Elevation in terrain can grant considerable advantages to those on the right side of the elevation.
In melee combat, any creature attempting a Shove attack on an opponent located higher on an incline has Disadvantage on that Contest. Creatures located higher on an incline receive Advantage on shove attacks against opponents located in a lower position.
In ranged combat, any creature attempting a ranged attack from a vantage point elevated at least 10 feet over his or her target receives Advantage on the attack and has their range increased by 10 feet. Creatures attempting a ranged attack on an opponent elevated at least 10 feet over him- or herself have Disadvantage and has their range decreased by 10 feet.

Difficult Terrain

Some terrain is difficult or painful to traverse. it can hinder both you and other creatures attempting to move inside its bounds. This is true during Travel (see below), but also during exploration combat.

Difficult Terrain in Combat

Combat rarely takes place in bare rooms or on featureless plains. Boulder-strewn caverns, briar-choked forests, treacherous staircases--the setting of a typical fight contains difficult terrain.
Every foot of movement in difficult terrain costs 1 extra foot. This rule is true even if multiple things in a space count as difficult terrain.
Low furniture, rubble, undergrowth, steep stairs, snow, and shallow bogs are examples of difficult terrain. The space of another creature, whether hostile or not, also counts as difficult terrain.

Dangerous Terrain

Some terrain goes beyond merely difficult and should be considered dangerous. Perhaps its surface is slippery, such as icy bricks or terrain affected by the Grease spell. Perhaps it is a thin ledge, such as a narrow beam or a castle battlement. It might be a steep incline, such as a palace roof. Regardless, it poses threats to creatures attempting a traversal -- usually the threat of falling.
If the terrain is solid, but slippery, the threat of falling might simply result in going Prone. If you fall from a height, however, you could take significant bludgeoning damage.
All dangerous terrain is considered difficult, and moving through 1 foot costs 2 feet of movement. However, it also contains additional dangers. While adventuring, the GM might require you make a Dexterity check to successfully pass through the area. If you fail, you fall.

Dangerous Terrain in Combat

While standing on dangerous terrain in combat, you have Disadvantage on all attacks.
Additionally, when you pass through the area, you must make a DC 10 Dexterity saving throw or fall. If the dangerous terrain is created by a spell, such as the Grease spell, the DC of the saving throw is the caster's spell save DC, instead.

Damaging Terrain

Beyond being difficult to traverse, some terrain is inherently damaging by its very nature. Moving through a thorn bush, or a puddle of acid or lava, will do damage of the appropriate type at the discretion of the GM based on terrain's nature.

Terrain and Travel

Certain types of terrain are easier or more difficult to traverse during travel. See the Land Use chart below for travel speed on different types of terrain.

Land Use

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Land Type	Slow Speed (mph)	Normal Speed	Fast Speed	Navigation DC	Use	Weekly Revenue	Development Options	Development Cost / sq mile	Development Time / unit	Development Result	Developed Additional Weekly Revenue
Forest	1	2	3	10	Hunting / Logging	5 gp	Clearing	200 gp	2 weeks	Plains	-
Plains	2	3	4	5	Foraging	3 gp	Irrigation	600 gp	4 weeks	Farmland	+20 gp
Hills / Mountains	0.5	1	2	15	Quarrying	2 gp	Mine Construction	4000 gp	8 weeks	Mine	+50 gp
Jungle	0.5	1	2	15	Foraging	4 gp	Clearing	400 gp	4 weeks	Plains	-
Swamp / Marsh	1	2	3	10	Foraging	2 gp	Draining	800 gp	6 weeks	Plains	-
Desert	2	3	4	20	Foraging	1 gp	Irrigation	1200 gp	6 weeks	Farmland	+20 gp
Settlement	1	1	1	10	Taxation	100 gp	-	-	-	-	-
+ River	See vehicle stats	See vehicle stats	See vehicle stats	-10	Trade	+10 gp	Mill Construction	2500 gp	4 weeks	Mill	+40 gp
+ Road	+1	+1	+1	-10	Trade	+5 gp	-	-	-	-	-
+ Caves	-	-1	-1	+10	Mining	+5 gp	Mine Construction	3000 gp	6 weeks	Mine	+50 gp
+ Coastal	-	-	-	-5	Fishing	+2 gp	-	-	-	-	-
+ Arctic	-	-	-1	+5	Foraging	-1 gp	*Irrigation, Mill Construction Impossible*	+200 gp	+1 week	-	-