They could be:
Latitudes and longitudes,
Gridlines,
Isobars, isotherms, contours,
National or regional boundaries.
Called both Elevation Lines or Contour Lines
The lines that connect points having the same elevation are a kind of isopleth called contour lines, or contours.The closer that the lines are on the map the steeper the terrain is.
boarders
Rivers
Topographic map
A legend describes the meaning of lines, symbols and colours used on the map.
contour map, comtour lines, canal..
No, it is not. A contour drawing is what you are referring to. Contour lines are the latitude and longitude lines on a map to find coordinate points.
A contour map, shows lines of equal elevation which look like tree rings all over the map, and is used to show elevation as well as slope and gradient information. The closer the lines are together, the steeper the terrain is in relative terms.
Parallel lines found on a map correspond to latitude.
The Glossary
A map reference indicating a location in terms of a series of vertical and horizontal grid lines identified by numbers or letters.
There can be various lines on a map, but the ones you are probably thinking of are 'latitude' and 'longitude'.
longitude
On a map, longitude lines go up and down, AKA vertically. Latitude lines are horizontal lines on a map.
The lines are what determines the absolute location of a place on the map.
A topographic map.