Sprayed cellulose lacquer (a hard gloss or satin finish). The standard factory finish for many woods. 
            Hand waxed (a soft finish which can be scraped off with a fingernail ) popular on stripped and reproduction pine
            Oiled (low shine finish) usually a preparation such as Danish oil.
If your furniture is less than about eighty years old and has it's original finish, it is likely to be one of these. 
 They can all be repaired, 

 Cellulose Lacquer is the most durable of the finishes and requires the least maintenance. Simply dusting, and wiping up spillages with a damp cloth are all that is normally needed. It can cope with heat from a coffee cup but not much hotter, so mats are a good idea. Extreme heat can fog the lacquer as can prolonged exposure to moisture. 

 Most solvents won't affect it but acetone, or nail varnish remover will. Lacquer is the hardest finish to repair but damage can usually be improved, if not removed completely.

 Cellulose is extremely fast drying which is useful if there are only small areas to repair. Minor damage can be built up in stages and cut back. Larger areas can be smoothed out if needed, but it is not possible to completely re-finish cellulose lacquer in the home. This is because it is a hazardous material to spray, and dries too fast for application by brush. If the lacquer is beyond repair, you may still have other options.

 Hand waxed finishes look good  but are the most susceptible to damage. Small marks, dents and scratches are inevitable but, once you have acquired a few, they become "patina" and a little wax blends them into the background. 

Wax finishes do need a bit of home maintenance. A fresh coat of soft beeswax (not a spray) should be applied to tops periodically to keep them protected. Once a year is ideal but, provided they still buff to a shine, you probably still have enough. Dining and coffee tables need particular care as wax marks easily with water. Spillages must be wiped dry immediately to prevent this. 

Beeswax has a chemical reaction in contact with moisture which results in a white bloom. While this is unsightly, and best avoided, it is rarely a major problem. Provided there is enough wax on the surface, the marks will just be in the finish and not the wood. Sometimes it can be blended back in: otherwise, the wax can be removed.

 These are the same waxed samples buffed up.

 Oiled finishes are generally hard wearing and practical but, like wax finish, they also require periodic maintenance.There are several varieties, ranging from pure oils, such as tung or linseed, to preparations like Danish or teak oil. What they have in common is an organic base rather than a mineral one. Unlike a lubricating oil, they dry to a film. The pure oils tend to need more coats and have a longer drying time. Preparations vary. Most have accelerators and some add a little polyurethane for a thicker finish.

Oils are the most scratch resistant of the finishes. Many scuffs will cover with a drop of oil or, at worst, may need to be sanded and re-oiled. They also resist water, which is why they are commonly used on flooring, kitchen work tops and garden furniture.

The finish doesn't stain with water but it can be dulled by it, and the  grain can be raised. It can be marked with oils, spirits and corrosive substances like bleach. Stains which have got passed the surface need removing before re-oiling otherwise they can be locked in.