In vanilla Minecraft, there are three dimensions: Overworld, Nether, and the End Dimension. When players spawn in a Minecraft world, they are in the Overworld. This is the only dimension in Minecraft where daylight cycles happen and time flows. On the other hand, there is no day or night in the nether and end dimension. Hence, it is always dark.
To access the other two dimensions, players need to go through their respective portals. For example, they need to go through the nether portal to enter the Nether. To access the end dimension, players must use an end portal, where all twelve eyes of the ender are present.
The end portal cannot be made by the player in survival mode and can only be found in Strongholds. This article dives into how players can build the Nether portal and End portal in Minecraft.
Portals are doorways in Minecraft
Building a Nether portal