Orienteering maps and Control Descriptions are produced to specifications written by the International Orienteering Federation (IOF).
The symbols used on standard control description sheets are explained in the attached IOF specification document (see the bottom of this page).
The full IOF specification (with diagrams showing examples of what a given set of symbols may look like on the ground are at this link on the IOF site.
Orienteering maps use standard specifications for depicting features and landscapes. For newcomers to the sport, one of the potentially confusing mappings is the use of white space to represent runnable forest. Full details of map specifications are at this link on the IOF site.
Sprint Orienteering (also Urban and City Orienteering) use different map specifications: Sprint Map specifications