Varnishes are tough, hard wearing and easily cleaned. Wood varnish is generally more durable than a wax or oil but is not as easy to maintain or repair if it becomes worn or damaged.
The retail market tends to search for Varnishes while the trade often refers to these products as Lacquers. Our lacquers section includes more solvent-based lacquers which tend to be used more by the trade. Varnishes are mostly water-based products which are recommended for use in the home.
In a word, no. The trade tends to refer to them as "lacquers" and the public tend to refer to them as "varnishes", but they are ultimately the same thing.
In simple terms yes. Care must be taken however when applying the first coat of varnish over the stain. If using a brush or roller the first coat of varnish should be lightly applied and not overworked by repeated brushing or rolling. Excessive working of the varnish on top of the stain will re-hydrate the stain and may result in the dragging of the colour or the colour becoming intermixed with the clear varnish. A way to avoid this is to use solvent-based stains under water-based varnishes or water-based stains under solvent-based varnishes.
In the early days when water based varnishes were first introduced to the market they were a pale comparison to their solvent-based alternatives. Over the decades the formulations have been vastly improved and they are now as good if not better than many solvent based varnishes. For example, water-based varnishes tend to be clearer (not like the old toffee-apple varnishes of the 60's and 70's) are much less smelly to use in confined spaces, and are safer for both the user and the environment. Many of the toughest and most durable varnishes available today are water-based.