The scale of a bass refers to how long the bass is from the bridge to the nut the vibrating length of the strings.
The length of the strings, or scale, is related to the quality of tone you get from the strings. The lower the pitch you need, the longer a string you want. That’s why guitars, which play higher pitches, are shorter than basses.
The most common scale for an electric bass is 34”. This is called ‘long scale’. Some basses, especially 5-strings, are 35” scale. Extra long scale is longer than 34”. Other basses are ‘medium scale’ 30"-33” and others are ‘short scale’ 30” or less.
As the scale length increases, the notes are spread further apart along each string. The further apart the notes are, the more stretching and shifting around will be required to play them. So, there is a balance of scale length and playability. A scale length of more than 35” begins to be uncomfortable to play unless you have huge hands.
A 34” scale bass is fine for a 4-string bass.
For a good-sounding low B string on a 5-string bass you should seriously consider a 35” scale bass. It makes a big difference. That low B won’t be so flabby and it will ring more clearly.
If you have really small hands or the bass is for a child under 12, you might consider a short scale bass.
In my experience with my students, most people who think they have small hands don’t. Playing bass is not natural to the human body. It will probably be a little uncomfortable at first. Your hands will slowly get accustomed to the stretching required. It’s not as bad as it seems at first.
If you do have small hands or the bass is for a child, try out some short scale basses. They have a little different tone to them. Paul McCartney played a short scale bass in the Beatles. I can only describe the sound as plinky, but I don’t mean that in a negative way. The tone of a short scale bass just has a different color to it. And, of course, the sound depends on the specific bass and the player playing it.