It depends on the time signature. In a 4/4 time signature, it has a value of 4 beats, while in 2/2 it has a value of 2 beats.
Explanation:
You need to understand how time signature affects the score so you won't get confused when trying to name the value of a rhythmic figure.
Let's start by looking at the "Rhythm Tree", with the Whole note at the beginning; each note divides into 2 notes, both of which are half the value of the original note. (See attached image noº 1, keep this in mind for later)
Then, we need to know the meaning behind the two numbers of the time signature (see attached image noº 2).
The top number indicates the amount of beats per measure.The bottom number (usually a power of 2) indicates which note constitutes one beat.*
* This is where the Rhythm Tree becomes relevant.
Basically, the bottom number is telling us how many times was the Whole note divided (or "branched off").
As for the 4/4 time signature:
The top number is 4, so... 4 beats per measure.The bottom number is 4... And what do we get if we divide the Whole note in 4 equal parts? That's right: Quarter notes, this is the note that gets the beat, meaning, 1 beat equals 1 quarter note.
This leaves us with the following values: A whole note equals 4 beats, a half note equals 2 beats, a quarter note equals 1 beat, an eighth note equals a half (1/2) beat, a sixteenth note equals a quarter (1/4) beat, and so on... (Same with rests)
Therefore, in a 4/4 time signature, a measure equals 4 quarter notes, or any combination of notes that has the equivalent value of 4 quarter notes:
A whole note (4 beats)2 half notes (2 beats + 2 beats = 4 beats)1 dotted half note and 2 eighth notes (3 beats + 2 half beats = 4 beats)4 quarter notes (1 beat each = 4 beats)1 quarter rest and 3 quarter notes (1 beat + 3 beats = 4 beats)1 quarter note and 6 eighth notes (1 beat + 6 half beats = 4 beats)16 sixteenth notes (1/4 beat each = 4 beats)1 half rest and 2 quarter notes (2 beats + 2 beats = 4 beats)2 quarter notes and 1 half note (2 beats + 2 beats = 4 beats)
And so on... There are many ways you can combine rhythmic figures in a score to match the values indicated by the time signature besides these examples, just make sure that they amount to the same value as 4 quarter notes per measure.
So, why is the value different in other time signatures, such as 2/2?
Let's break this down:
The top number is 2, so... 2 beats per measure.The bottom number is 2... And what do we get if we divide the Whole note in 2 equal parts? That's right: Half notes, this is the note that gets the beat, meaning, 1 beat equals 1 half note.
This means that the whole note, which has the same value as two half notes, equals 2 beats in a 2/2 time signature.
Hope this helped clear your doubts, feel free to ask if there's something you don't understand.
