Coco coir is the fibrous outer shell of a coconut. It's used as a soil-less medium to grow in hydroponically (drain to waste). It's not buffered, and provides no nutrients on it's own, meaning you'll need to ph/feed daily. Lots of coco growers around here that'd be better at giving you the ins and outs of coco growing. Don't let coco dry out is the best coco advice I can give you lol.
I'm a soil grower. I make my own organic soil and flower in small, 1 gallon pots typically. 1 gallons are tricky because there isn't enough nutrition, usually, in 1 gallon to sustain a plant through flower, so I have to supplement with nutes. BUT, organic soil is great for keeping a bunch of small vegging plants and clones going which is why I've stuck with it over the years.