The way Deltarune plays out is similar to Undertale and the other title inspired by it, Earthbound. You play Kris in what seems to be a normal day at school. After receiving a mission from Professor Alphys, you'll soon discover that things are not as simple as they seem.
The game has turn-based battles as well as screens where you have to get around the various dangers thrown into your character's path. In the battles you can see the influence of Undertale, as you've got a special command that lets you interact with your enemies in a nonviolent way.
Deltarune is a very special RPG that should dazzle fans of Undertale. It's got a delightful aesthetic typical of 16-bit titles and a terrific soundtrack that also includes music from Undertale.