Data structures are used to pass information between an application and the LAN Server APIs. Most APIs use data structures, and many data structures have more than one level of information available. Level 0 (zero) specifies the least information, and higher levels usually specify incrementally more information.

For instance, if you issue a NetServerGetInfo call at level 0, only the ASCIIZ name of the server is returned. If you issue the same call at level 3, the returned data structure will contain 47 entries: the name of the server plus all level 1 and level 2 data, including the number of users allowed on the server, server heuristics, and so on.