Varactor Diode Video

Varactor Diode is the same as a Varicap diode, the former name probably being more common these days.
Because the diode junction diffusion zone widens with reverse junction current, any diode or PN junction (commonly LED or BC557 Collector-Base junction) can be used.
The genuine part number devices though, such as MA4ST2600 I used as an example in the hand written board notes will have published data to guide the designer toward a final circuit.
This video from Youtube is very good at explaining many things you need to know about Varactor diodes.