Credits

Credits are used as universal currency in this game. There are two achievments related to earning Credits.

Getting Credits
You can get Credits numerous ways.

Selling goods
Most of Resources (except Gravel, Silicon…), all Upgrade Kits and upgraded vehicle parts can be sold to Merchant NPCs, Market Warehouses and NPC Outposts. Trading dialogue will usually open by left clicking suitable object.

Exploring the world
While exploring the game world, you will receive some Credits as reward for certain discoveries.

Resource deposits
Discovering Resource deposits will reward you with small amount of Credits. Exact amount depends on Resource type and deposit size. Most of small deposits will not reward you at all. Medium deposits will most often reward you with 0.100 Credits, which is the lowest amount you can get as reward for Resource deposit discovery. Large and Huge deposits will reward you even more. Few examples: Keep in mind that size of deposit covers some span, so reward for discovering same size and same Resource type deposits may vary a little.
 * Small Coal = 0 Credits
 * Medium Copper = 0.100 Credits
 * Huge Cobalt = 0.232 Credits
 * Huge Iron = 0.373 Credits
 * Medium Silever = 0.617
 * Huge Uranium = 0.754 Credits
 * Huge CaF2 = 0.825 Credits
 * Huge Titanium = 1.15 Credits
 * Large Platinum = 1.29 Credits
 * Medium Coal = 2.07  Credits
 * Medium Niobium = 3.40 Credits

Multiple Resource deposits at once can be discovered by Scanning pulse ability.

Apparently discovering source of geothermal heat will not reward you with any Credits.

Biomes
Discovering a new Biome will reward you with 5 Credits. This is however somewhat limited source of Credits, because there are only 27 Biomes in game, so only 135 Credits can be earned this way.

Market Warehouses
Discovering a Market Warehouse will reward you with 10 Credits.

Artifacts
Discovering Artifact will reward you with 50 Credits. Each artifact will give you this reward, no matter you have discovered (or even researched) this Artifact type already.

Mining Credits
Each Science lab building is capable of mining Credits. This option is off by default and must be manually activated. Lab will only mine Credits while it is not performing any research. However once you activate Credit mining, the option will stay active and if nothing is researched, the lab will automatically mine Credits until you uncheck it. While mining Credits, the Lab consumes 100% power, so if you suffer from power shortage, turning Credits mining off may help a lot. There is some inventory space for Credits in Outpost or Lab, but if you want to collect Credits mined by Lab, you have to place Storage Container, refit it to Credits and click on "Take" button. For some unknown reason amount of Credits stored in Storage Container is not show in Continers info tab. Amount of stored Credits can be found in Outpost stats or simply by collecting them by clicking on "Take" button.

Spending Credits
Similar to getting you can spend your Credits to buy Resources and Upgrade Kits at Merchants, Market Warehouses and NPC Outpost.

They are also useful to bribe pirates when they come to attack you.

You can buy Transmitter item from specific NPC for 1 Credit.

Disclaimer
Information on this page come from my single player server experience. They may be incomplete and slightly different from multiplayer game experience. Game version 19.09.01.1. Also I am not a native English speaker (you surely noticed already ;-) ), so feel free to correct me.