Help Understanding libgdx create animations example game

I am trying to understand the example game, cuboc. GitHub is https://github.com/libgdx/libgdx-demo-cuboc. I have generated my texture atlas but I do not understand the code that uses this texture atlas. Here’s the code (you can see on github too here:

package com.badlogic.cubocy;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.FPSLogger;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Animation;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.SpriteCache;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import com.badlogic.gdx.graphics.glutils.ImmediateModeRenderer20;
import com.badlogic.gdx.math.Vector3;

public class MapRenderer {
...
    private void createAnimations () {
        this.tile = new TextureRegion(new Texture(Gdx.files.internal("data/tile.png")), 0, 0, 20, 20);
        Texture bobTexture = new Texture(Gdx.files.internal("data/bob.png"));
        TextureRegion[] split = new TextureRegion(bobTexture).split(20, 20)[0];
        TextureRegion[] mirror = new TextureRegion(bobTexture).split(20, 20)[0];
        for (TextureRegion region : mirror)
            region.flip(true, false);
        spikes = split[5];
        bobRight = new Animation(0.1f, split[0], split[1]);
        bobLeft = new Animation(0.1f, mirror[0], mirror[1]);
        bobJumpRight = new Animation(0.1f, split[2], split[3]);
        bobJumpLeft = new Animation(0.1f, mirror[2], mirror[3]);
        bobIdleRight = new Animation(0.5f, split[0], split[4]);
        bobIdleLeft = new Animation(0.5f, mirror[0], mirror[4]);
        bobDead = new Animation(0.2f, split[0]);
        split = new TextureRegion(bobTexture).split(20, 20)[1];
        cube = split[0];
        cubeFixed = new Animation(1, split[1], split[2], split[3], split[4], split[5]);
        split = new TextureRegion(bobTexture).split(20, 20)[2];
        cubeControlled = split[0];
        spawn = new Animation(0.1f, split[4], split[3], split[2], split[1]);
        dying = new Animation(0.1f, split[1], split[2], split[3], split[4]);
        dispenser = split[5];
        split = new TextureRegion(bobTexture).split(20, 20)[3];
        rocket = new Animation(0.1f, split[0], split[1], split[2], split[3]);
        rocketPad = split[4];
        split = new TextureRegion(bobTexture).split(20, 20)[4];
        rocketExplosion = new Animation(0.1f, split[0], split[1], split[2], split[3], split[4], split[4]);
        split = new TextureRegion(bobTexture).split(20, 20)[5];
        endDoor = split[2];
        movingSpikes = split[0];
        laser = split[1];
    }

What I do not understand is what is split used for? Like, what is going on here:

split = new TextureRegion(bobTexture).split(20, 20)[1];

And sometimes it looks like split is a method that takes two int‘s, 20 and 20? Why 20?
Othertimes split is used as an Array like in …

rocketExplosion = new Animation(0.1f, split[0], split[1], split[2], split[3], split[4], split[4]);

… and I just can’t follow what’s going on here. Thanks!