Dear Allwyn,
This is masking tape and available with the all the hardware stores and reputed paint stores. There are many type of masking tape available in the market, according to size and quality. This has multiple uses but mainly used to get super sharp paint line. When painting or varnishing around the home, the use of masking tape will help speed up the painting work and prevent mixing of paint color where it should not required.
Regards
S.L. Gupta (Civil Engg. {Retd.})