Bedrock, or Bedrock Edition, is the version of Minecraft that brings together consoles, iOS/Android, and Windows 10. Bedrock originated as "Pocket Edition" (MCPE/PE), as it was originally only available on mobile devices.
Are Bedrock and Pocket Edition the same?
Yes. While the game has evolved, Mojang has since updated the name. Collectively, most versions of Minecraft that are not the Java version fall under "Bedrock".
So what is PocketMine?
PocketMine-MP is not an edition of Minecraft, rather it is server software that was built prior to Mojang's release of the Bedrock Alpha Server in the early days when Bedrock was still known as Pocket Edition. While it remains the most popular alternative for some, it is unlikely to offer the most recent versions of Bedrock and/or the same features you may expect to see.
What about Realms vs Bedrock Alpha Server?
Realms are servers offered directly through Mojang. Realms are proven to offer less customization and less-than-stellar performance; however, the experience overall may be more convenient, especially for console players.
We recommend Realms for the following players:
Nintendo Switch players
Parents with younger children wanting to play
Any console players who want the most convenient experience
Any players interested in Realms-specific perks
Any server owners who want the most convenient experience for friends/community playing on console
If server performance is critical to you and/or the above points do not apply to you, we recommend the Bedrock Alpha Server (BDS) over Realms. Through Bedrock content creators and personal testing, we've found that BDS offers much smoother and stable gameplay when combined with the proper resources.