Web Feature Service

Although the result looks completely different, sending requests to WFS works pretty much the same as the WMS output options, except for the URL format. There are a few big differences here; notice that the format parameter name changes to outputFormat:

http://localhost:8080/geoserver/topp/ows?
service=WFS&
version=1.0.0&
request=GetFeature&
typeName=topp:states&
maxFeatures=50&
outputFormat=csv

CSV

This is the most common form of data exchange, but not likely the one you'd want to use unless you're planning to import into a spreadsheet (that is, Microsoft Excel) or for importing into an external database where other layer output formats don't apply.

The output format is specified by csv as the outputFormat parameter value.

GML (plain text)

This format seems to be overshadowed by the more popular KML format from Google. The KML format is somewhat based on GML; a GML output file can be converted to KML, but it's always the other way around. Both formats are...