Pixels are the currency item in Starbound and they are used in most of the crafting recipes. Initially you will get a small amount of pixels from completeing quests, you can also get pixels by defeating monsters with any weapon other than a bow or hunting knife. There are pixel containers which can be found undergound or even near the surface, when broken they yield a random amount of pixels. You may also find pixels inside chests or other containers. Once the player has unlocked the Steel crafting tier they will be able to craft a refinery machine; this machine can convert ores or bars into pixels, but you can not convert coal or alloy bars.

Copper bar = 10 pixels
Silver bar = 30 pixels
Gold bar = 50 pixels

So it may still be useful to mine the copper ores even after you have passed the first tier of character progression as they can always be converted into pixels.

Whenever the player dies or is killed they suffer a 20% pixel loss, this is currently the only death penalty aside from being respawned on your ship or possibly on the planet's landing spot. Currently the only method to store pixels is to use a pixel compressor machine that creates Voxels, this imposes a 40% loss in pixel value when the Voxel items are refined back into pixels. Voxels can be created in 1k, 2k, 5k or 10k denominations; which would be worth 600, 1.2k, 3k or 6k respectively.

Pixels are the only requirement to craft items with the 3d Printer found on your ship. In order to print an item you would first need to scan an item of the type you want to craft, it will cost some pixels to do the scan and the scanned item will be lost in the process. In most cases I think it's much simpler to loot the items you want from NPC structures as print them yourself. Many of the building blocks available in Starbound have to be obtained in this way. If you wish to loot blocks from an NPC village you may need to kill all the town gaurds, the other NPC citizens such as merchants will not be aggressive towards you.

And lastly I should mention the skyrails which would enable you to travel very quickly around a planet if you have enough of the durasteel rails.