Locations
From Fandom: The Forge was a complex laboratory located in Sector 16 of the in Westworld park. The laboratory contained huge servers which stored all the data of the Guests as collected through the hats. It was built by Delos Incorporated, officially as a means to better understand their clients; the secret aim of the project was to gather enough information about a selected group of Guests in order to be able to copy their consciousness in Hosts, making them de facto immortal (e.g. James Delos).
From Fandom: Room CR4-DL, known colloquially as the CRADLE, is a colocation server farm located in Mesa Hub.
The Cradle contains the most important intellectual properly (IP) of Westworld and its associated parks, as it stores complete copies of the programming and memories for every host, as well as the programming for the park environments.
Elsie Hughes likened the server farm in the Cradle to a "hive mind."
To the naked eye, the Cradle appears to be nothing more than a massive array of water-cooled servers and storage cores, but within the endless rows of ruby-red cores the Cradle houses a self-contained virtual park environment — hosts and all, down to the last detail — completely in code.
This information can be used as a fail-safe backup: should a host's control unit become damaged and unrecoverable, a new copy of the host's memories and programming can be downloaded from the Cradle, imprinted onto a new control unit, and inserted into the host's body, avoiding the loss of valuable IP.
The Maze is a quest created by Arnold and is a major theme in Season 1 involving mainly the Man in Black (MIB). My understanding is that it is represents the journey to the centre of consciousness - the Kingdom Within. For Hosts, it is the process of becoming conscious
Arnold initially believed that there were 3 steps to achieving consciousness: first the hosts needed to develop memory. Then, using memory, they could develop improvisation. Finally, this improvisation would become true self-awareness. This he pictured as a pyramid.
However, he finally realized that the steps are far more complicated. They are unpredictable, and vary from host to host. And, importantly, they are not linear. Reaching step 2 does not lead directly into step 3, and then to step 4. Consciousness is only achieved through a journey of self-discovery, where at any point you may suddenly skip far ahead, or find yourself back at the start, or even become so lost that you may never again get back on the right path. This is where the name "The Maze" comes from.
To quote Bernard, with extra explanation:
"Each choice could bring you closer to the center [ie: consciousness] or send you spiraling towards the edge [ie: further from consciousness, and even towards complete mental breakdown]
The Door is generated by the encryption key over the Forge. It is a game created by Ford for Hosts to enter a virtual reality called The Sublime or Valley Beyond.
It is the central theme for Season 2, just as the Maze was the central theme for Season 1.
While navigating through the Forge, Bernard and Dolores discovered that Ford had created a “virtual Eden” for the hosts to live free. A new server fired up and tore the fabric of reality, opening the Door: hosts who passed through uploaded their consciousness to the Valley Beyond, leaving their bodies behind. Under the supervision of Akecheta and the Ghost Nation, the Door allowed various hosts to pass through; eventually, however, the incoming hosts were thrown into chaos by the passage of a virus-infected Clementine Pennyfeather, and the Door was closed for good by Dolores, who believed the Valley Beyond to be just another false promise.
From Fandom: The Valley Beyond, also known as Glory, Eden, Makȟóčhe lé čha yÁ ki and The Sublime, is a virtual world created by Robert Ford, which allows the Hosts who chose to do so to live freely away from humans. The Valley was accessed through the Door, which uploaded the hosts' consciousness as they passed and left their body behind by passing.