Altered Carbon season 2 has finally arrived two years after the show debuted on Netflix, which means that even fans of the show may have forgotten what all the sci-fi terminology and jargon means. Starring Anthony Mackie as Takeshi Kovacs, the role previously played by Joel Kinnaman, Altered Carbon season 2 moves the action to the colony planet Harlan’s World, where Takeshi was born.

Based on the books by Richard K. Morgan, Altered Carbon is set around 400 years in the future. After first arriving on Harlan’s World, humans discovered technology from a lost alien race that was used to create stacks: disks on which a person’s mind can be stored in the form of code. If a person dies, their stack can be put into a new body and woken up again, creating the potential for eternal life. Inequality persists, however, and while society’s wealthiest have a ready supply of beautiful backup bodies, most people have to settle for what they can afford - or else be left in limbo until their stack finds a new home.

If you’ve forgotten what a DHF is, what it means to be spun up or spun down, who the Meths are, the dangers of double-sleeving and how to avoid your stack getting fragged, here’s our handy glossary for Altered Carbon’s sci-fi world.

  • Archeologue - Scientists who studied Elder artifacts recovered on Harlan’s World. Angelfire - A lethal energy beam fired by the orbitals surrounding Harlan’s World. Array - Similar to the Cloud, this is a satellite network where everything from virtual reality constructs to backup DHFs can be stored. Backups - Stored copies of a person’s DHF that are activated inside a new sleeve when a Meth is killed. Coils - Synthetic enhancements that allow the user to interact with surrounding technology. Construct - A virtual reality environment. CTAC - Colonial Tactical Assault Corp. A Protectorate force who needlecast into many different sleeves on many different worlds. DHF - Digital Human Freight. A human mind and memories stored in code, usually on a stack. Double-Sleeving/Multi-Sleeving - Having copies of a person’s mind in more than one body at the same time. Highly illegal and punishable by death. Elders - An ancient race of advanced aliens, believed to be extinct, from whom humans acquired the raw material for making stacks. Envoy - An elite rebel fighter trained to have total control over their mind and body. Frag - When a person’s DHF becomes corrupted or damaged, often as a result of resleeving too many times. Meth - Those who are elite and wealthy enough to have backups of their DHF and clones ready to be woken up in the event of their death. Named after Methusaleh, a Biblical figure said to have lived to the age of 969. Meths’ extremely long lives usually result in diminished empathy. Needlecasting - A fast method of interstellar travel, achieved by transmitting one’s mind from a body on one planet to a body on another. ONI - Online Network Interface. A mini-computer installed in a person’s eye that allows them to make and receive calls, record and transmit video, and look up information. Orbitals - Weaponized satellites that surround Harlan’s World, created by the Elders. Protectorate - The military force of the UN, which maintains order across the Settled Worlds. Quellists - Rebels who follow the teachings of Quellcrist Falconer. RD - Real death. When a person is killed in such a way that their stack is also destroyed. Renouncers - A cult of people who have renounced their physical bodies and chosen to live inside an idyllic construct. Resleeve - To have one’s stack put inside a new body. Settled Worlds - Human-inhabited planets. Sleeve - A body, either organic or synthetic. Songspire - A mysterious species of tree that was cultivated by the Elders. Stack - Cortical stack. A disk made from the alloy found on Harlan’s World, in which a person’s DHF is stored. Stacks are installed at one year old and found at the top of a person’s spine. Stronghold - The former base of Quellcrist Falconer’s resistance group. Synth - A synthetic sleeve. Spin Up/Spin Down - To wake up a mind in a new body, or conversely to take a mind out of a body.

More: Why Altered Carbon Recast Joel Kinnaman’s Takeshi Kovacs For Season 2