a long string which contains information on how to build a level. This information contains tiles and objects such as enemies and can be decoded and displayed in Ned or N's userlevels mode. See map data for more information on how maps are encoded.
a level that is created based on information in this string and can be played in Ned or N's userlevels mode. (This is what "map" means in most cases. The string is called "map data". On this wiki, "map" always means a level.)
It is important to distinguish between level and a map. A level is one of the 500 maps which come with N. The 157 userlevels which do also come with N 1.4 nevertheless are maps because these ones aren't an integral part of N. Userlevels are maps which are saved in your userlevels file.
(If you don't agree in this definition of the terms "level" and "map", join the discussion about this article.))