A virtual cache refers to certain kinds of hidden points or caches in geocaching systems.
Techopedia explains Virtual Cache
Geocaching is an activity where users take geosensitive software and devices into the field to use geo-position signaling to locate specific destinations. In many cases, they reach their destination to find a physical hidden item or "physical cache." However, sometimes, instead of a physical item, there is just a virtual marker that may show up on an interface or dashboard such as, for example, an icon. This is a virtual cache. Although virtual caches have largely become obsolete, other tagging technologies can preserve this kind of geocaching tradition.
In some cases, IT experts may also use the term "virtual cache" to refer to a virtual memory cache that may be applied to virtual systems or to a memory cache that uses a virtual address.
This definition was written in the context of Geocaching