If you want to understand maps better (be it historical or modern), it is helpful to know some lingo. Here are the most common terms that every map enthusiast should know:

Cardinal Direction — the four primary directions of North, South, East and West
Boundary — a line that marks the limit or edge of one place and another, such as a state or country
Cartesian Coordinates — using an X and Y axis and their intersections to plot specific points on a map
Cartography — the making and studying of maps
Cartouche — the frame around the title of a map, historically ornate and scroll-like and displays the name of the map or mapmaker
Citation — place on a map (usually in a corner) that lists information crediting the mapmaker, as well as the year it was made, the source of the data, etc.
— written descriptions on a map or within it’s borders that discuss aspects of the subject matter.
Compass Rose
 — a circular figure (decorative or simple) that displays the orientation of the cardinal directions and their intermediate points. In early map designs it resembled a rose.
Contour Line — lines spaced close together or far apart to indicate land levels or elevation
—  the line or course on which something is pointing or facing.
 — The height of a point or an object above or below sea level. Also referred to as altitude or height.
Grid — the parallel intersecting lines and corresponding numbers that provide reference to specific points on a map.
— Also called a pictogram, it conveys meaning through a pictorial resemblance to a physical object.
Inset map — a smaller, usually simplified, map found inside the main map which shows the location of the main map in a larger scale.
Latitude — a horizontal line on a map indicating how far north or south a point is from the equator
Latitude — a horizontal line on a map indicating how far east or west a point is from the prime meridian.
Legend or Key — a guide to symbols, numbers and figures (usually with a brief description) appearing on a map.
Meridian — a line of longitude on a globe
Neatline — the edge of the map itself. It may be a single or double rule, a decorative edge or dashed border that encloses the map.
North Arrow — an arrow or similar symbol that indicates which part of the map faces North. Most, but not all, maps orient the map with North facing the top.
Orient — align or position relative to the points of a compass or other specified positions.
Relief — shading on a map to indicate dimensional changes in elevation (height and depth) 
 — a graphic device used to measure distance on a map. It looks like a little bar or ruler, with units marked equivalent to the map’s scale.
Spatial data
— information such as location, elevation, distance, etc. that establish and document the three dimensions of space
Survey — collecting information about the land by measuring its size and shape
Symbology — the use of symbols, icons and other graphic objects on a map to depict places or things in reality
Terra Incognita — the term meaning “unknown territory” used in exploration to denote any region unexplored or mapped
True North
— the direction to the Earth’s geographic North Pole
Voyaging Vehicles — the ships, cars, planes, trains, balloons and other conveyances depicted on a map
Winds and Wind Blowers or Faces
— often shown on maps from the 16th century, represented by cherubic faces blowing air. They are: Boreas (from the north), Eurus (from the east) Nouts (from the south) Zephyrus (from the west).