The wither is one of the two boss mobs in Minecraft. In Java edition, it is less powerful than in Bedrock. In Java it has 300 health, the wither skulls do 5 damage in easy, 8 in normal & 12 in hard. Whereas in Bedrock, it has 600 health, and does the same damage with the wither skulls as in Java for my understanding & it has a dash attack that does 15 damage (Bedrock only). You can get more info here: https://minecraft.fandom.com/wiki/Wither