What a Stockroom label carries: which barcode prints, what the smallest sizes have room for, and how to add the bin location. Choosing a size and the fields to print is in Print barcode and price labels.
The barcode
Each label carries the fields you selected - title, variant, SKU, price - and, unless you unticked Include barcode, a barcode with its digits printed underneath. The barcode always uses the product's current barcode in Shopify at the moment you print, in its native format (for example EAN-13 or UPC-A). That means you can add or correct a barcode in Shopify at any time and simply reprint - the labels pick it up automatically, including on older purchase orders and orders imported from Stocky. If a product has no barcode saved in Shopify, Stockroom encodes its SKU instead, so new products still scan - a label showing the SKU under the bars is the sign that the variant has no barcode yet - and you can generate one from the same dialog - see Generate barcodes for products that have none. Printing on its own writes nothing back to your catalog.
The smallest label sizes
The smallest sizes have fixed layouts: the 1-inch-high labels (Dymo 30332, Zebra 1.25 x 1) print the price, a one-line product name, the variant, and the barcode. These two sizes - and the Zebra 1.25 x 1.25 - can also print the SKU on a line beneath the barcode digits, and the vendor beside it: tick Include SKU and Include vendor in the print dialog. Both are off by default here, so labels you already print are unchanged until you turn them on. The Dymo 30299 jewelry barbell prints price and SKU on one end and the barcode with its digits on the other, leaving the middle blank to wrap around a ring or chain - short barcodes (around 8 digits) scan most reliably at that size. Avery 5167's half-inch labels print price and barcode only.
Bin location
You can also add the item's Bin location to the label - it prints on the small detail line beside the brand, so it costs no extra space. Handy for restocking: the ticket says which shelf the item belongs on. Printing from a purchase order uses each line's destination; printing from a product uses the location picked in the dialog, and All locations prints the item's default bin.
Good to know
Where each field sits, and adding your own text or metafields, is set per size - or per preset - in the layout editor: see Change what prints on a label and where.