Luckily, Mojang has made installing a resource pack incredibly easy. The following tutorials are only for the Java and Windows 10 editions of Minecraft.

A Java pack converter for 1.21.4 version or higher to a Minecraft resource pack suitable for the Bedrock version of the game, as well as the creation of a geyser mappings file - FurrO2/java-to-bed ...

Since Minecraft is a sandbox game that can be modded, thousands of mods, texture/resource packs, and shaders have been released for it.

You can install mods in "Minecraft" by playing the "Java Edition" and using the third-party app Minecraft Forge.