There are 2 numbers in a time signature and look a lot like a fraction. The picture below explains what each number does in music.
Each piece of music will contain at least 1 time signature. It is found at the very beginning of the music. There can be time signature changes, but will come later in your musical experiences.
There are other time signatures as well. This will change the values of notes. See Note/Rest Values for a guide on how long they will be.