Drawing with Procreate
Procreate is an iPad app that’s used for drawing. It was specifically designed for use with the Apple Pencil. Procreate is not a free app, but it can be bought with a very low one-time payment.
Drawing in Photoshop
Photoshop is a graphics editing/creation program that has been around since 1990. It is owned by Adobe. The most recent editions of Photoshop are paid for on a subscription basis each month.
You can use a Wacom Tablet to make drawing in Photoshop a bit more natural-feeling. The Wacom tablet is a drawing pad that allows you to draw digitally using a stylus.
Drawing with Clip Studio
Clip Studio Paint is a graphics editing program released in 2001. It was originally created specifically for manga comic artists who create black and white art for print. Later editions allowed for the creation of full-color art. It is a popular program for professional illustrators to create digital artwork.
Older digital drawing programs
As technology comes and goes, older programs get replaced with newer, more robust drawing software. In the past, some of the commonly used apps for digital drawing included Microsoft Paint (also called MS Paint), and various oekaki websites that allowed users to make small, digital sketches in a web-based application.