A scale is a set of notes consisting of root and interval sequences. C-D-E-F-G-A-B-C is a scale with C as a root and has an interval sequence of 2-2-1-2-2-2-1. It's called the C Major scale.
The D Major Scale has the same interval sequence, but only the root becomes D. It's D-E-F#-G-A-B-C#-D. All the compositional notes went up by two semitones on the C Major Scale. It's like adjusting the key of a song in a karaoke room.
It's okay to study the type of scale later. For now, let's train only on the Major scale you encounter most often in your daily life.