Mankind's eternal questions Where am I? Where am I going? How do I get there? can, at least in a strictly literal sense, be answered by navigation.
The art of navigation developed with boat travel (hence the name from Latin navis – boat), but is also essential in air travel, space travel, and other modes of transport. Amateur travellers might need navigation skills when hiking, driving, or cruising on small craft, as well as space travel.
For orienteering when hiking, refer to orienteering and GPS navigation. Especially the latter is relevant also when driving and boating. The rest of this article will be about navigating on water.
Driving a boat in open waters in good weather seems trivial. And in fog and more complicated environments we have the GPS, haven't we? With good luck advanced navigations skills may be unnecessary most of the time, but the GPS will eventually fail, you will have erroneous GPS maps or you will get lost or stranded for other reasons.
Learning to navigate you will be able to handle navigation without much equipment, and also learn techniques to evaluate the output and advice of any tools, get the practice to use those techniques unconsciously or otherwise automatically and get a better understanding of your environment. Knowing the old ways and to get everything out of modern tools is also fun – and having a certificate on seamanship skills is often necessary to get to charter a boat without crew.
For the more seasoned boater, there may still be some surprises in foreign waters, such as tidal currents for those used to inland waters.
For any navigation out of familiar waters you need charts. For the ocean there are charts for most of the world from a few sources, while for coastal and inland waters you will mostly need local charts. There has been very much effort in standardization, but charts still differ, both in appearance and quality.
On any ocean coast there are tidal currents, which have to be taken into account by applying tables in sometimes complicated ways. The currents in rivers are self-evident, but there are also other kinds of currents, caused e.g. by wind and air pressure systems, like tidal currents much more pronounced in certain narrow or shallow passages.
There are many caveats with the quickly developing electronic navigation tools. In addition to the risk of total failure (sea water, even as found in cabin air, is bad for electronics, for one), there are many ways in which the tools work in a way not intuitive without much practice. Without professional equipment and advanced skills, you should be able to get by without the tools in any circumstances.