POS ('at the point of sale') systems are usually comprised of a computer, a software program and hardware (printers, barcode scanners, cash drawers) which are specifically designed for processing sales at checkout stations.
The 'computer' can be a desktop or hand-held device, Windows or Mac, but the deciding factor is 'the software' which must be written for either Windows or Mac. Apple does say that Windows programs will run on Macs if Windows and their Basecamp programs are installed. Some shops who have done that report that there's difficulty sometimes with printing.
POS computers are usually connected through a local network (Local Area Network (LAN)) to a host computer (main computer, server). The most common mistake is to use something other than a dual-band router to connect the computers (with Ethernet cables, preferably cat6 or cat7).
Thermal receipt printers print receipts (not labels) on 3" receipt paper. Consignment stores with 'no-return policies' may not need this expense because the receipts have no purchase (as far as returns are concerned). Regardless you'll find most software vendors more than willing to sell a receipt printer to a consignment store owner without first having this discussion.
Cash drawers with locks safely store money and reduce the temptation of theft (by anyone having access to the POS area). The drawer connects to the receipt printer and pops open when a receipt is printed. With Best Consignment Shop Software, if there is no receipt printer, the drawer uses a special adapter (which replaces the printer) to connect to the computer, allowing the drawer to be opened by pressing a key on the keyboard or when a receipt is printed for cash and check sales. As a convenience, the drawer will not open for other payment methods like credit cards, PayPal, gift certificate, etc.
Barcodes at POS are a must for any store that checks out many items daily. The alternatives (enter an unlisted item, chose from a pick list, enter the Item ID) are more labor intensive that just scanning a barcode to populate the invoice line with item information. With BCSS an inventory record can be found by scanning the barcode.
Labels can be printed in a variety of ways and formats. With Best Consignment Shop Software labels may be printer on plain paper, sheets of labels or rolls of thermal labels.
Small shops on thin budgets opt for the minimal-cost method of printing labels and tags with ink printers on slightly-heavier stock paper and cutting them out. This method can include barcodes.
For a bit more sophistication ink printers can be used to print labels and tags with ink printers on sheets of labels (office supply store) or hang tags (online providers). Labels are adhesive, can be removed from the sheet and attached to items. Hang tags are perforated and can be torn from sheets.
Any methods using ink printer involve the additional costs of higher per-label cost and high ink costs. There are also inherent risks of paper jams, out-on-ink runs and time spent trying to print on partially-used sheets.
Thermal labels are the preferred method when the initial cost of the thermal-label printer isn't an issue ($300+ or at resaleworld $400+). There is a wider variety of sizes and types of labels ranging from jewelry barbell labels to four by four shipping labels. The printed labels and tags give a much greater professional appearance.
Many vendors of POS systems will take more money from shops over time from 'support fees' than they will from the initial purchases of the systems.
Websites should be used to disclose important information and 'cost' is perhaps the most important consideration when choosing a system, yet we haven't see a website yet with every possible cost prominently displayed on a home page - with the exception of Best Consignment Shop Software which has no post-sale support fees.