Fleeceware: Apps which are marketed as “free”, but which then trick the user into subscribing for paid services (which are available free elsewhere), often for excessive fees.
Common examples are horoscope apps, QR code or barcode scanners, and face filter apps targeted at younger users. Publishers of fleeceware target users who may be less cognizant or sensitive to initial fees and reoccurring charges.
Often users are hooked in by free trials, which turn out to be difficult to extricate yourself from after the “free” period has lapsed.
These are currently most common on phone apps (both iPhone and Android), but the same techniques can be found with some desktop applications as well.