All metal edges that are used for cutting need to be sharpened at some point for them to retain there edge, no amount of technology will ever change that.
Hundreds of thousands of years ago, before man even discovered that he could obtain metal from ore he realised that his tools needed to have a keen edge to obtain best results.

Flint tools, the predecessors to metal tools were easy to sharpen; a new edge was worked onto the cutting face by striking the tool with another piece of stone.

Obtaining a keen metal edge was then, and is now a totally different process. As we all know from our school days each time you cut something with a metal blade the blades dulls very slightly. Different materials have a differing affect on the blade and by how much it dulls it.

As time went by man had to learn the art of sharpening an edge, initially this was achieved by stroking an edge across a very basic sharpening stone, which was nothing more than a stone!

Soon he realised that certain types of stone gave a better edge than others, coarser stones cleaned an edge up but didn't hone the blade sufficiently, likewise a fine stone honed the edge but only after much work. Still to this day many tools are still sharpened by using a stone although sharpening stones are a much more scientific piece of equipment.

Sharpening stones work by taking the surface off of the edge of a cutting tool, with prolonged use the cutting edge of a tool rounds over and needs to be honed. Not all metals are the same, some are better at holding their edge than others, if a metal is too hard it will take an eternity to sharpen but will hold it's edge for longer likewise if a soft metal is used the edge will be achieved easily but will dull easily, so it's very important that the correct steel is used for the tool.

Woodworking tools are usually made with steel that is easier to sharpen hence the steel is a little softer than the steel that goes into making a pair of garden shears or household scissors.

Craft, scalpel and razor blades are made from extremely hard steel that would take the normal man in the street an eternity to hone, hence why these are throw away products.

Sharpening stones generally need oil or water to help work the steel, a few drops of either applied to the stone during the sharpening process help to achieve a sharper edge quicker. Using too much oil will make your knife blade glide over the surface of the stone and will prevent the stone from sharpening your edge.

Because dirt and dust can load an oilstone just as much as sharpening dust and metal particles, always keep stones covered and in a clean place between uses. Sharpening stones are available in many grades, from a very coarse 100 grade all the way down to a fantastically fine 12000 grade Japanese stone.

Diamond stones are now also very popular for sharpening; these are a lot more ferocious than a stone and need to be used properly. Where a sharpening stone may take ten to twenty passes of a blade to sharpen it, a diamond stone could take only three or four passes. Diamond stones don't generally need any oil to help the process although some people do apply a drop or two.

Diamond stones are also available in differing grades to suit all sharpening jobs. The benefit with diamond is that it's much easier to get a specially manufactured diamond stone for a specific application.

Generally sharpening stones come in uniform sizes, usually eight inches by 2 inches by one inch, because diamond stones are normally an applied strip of diamond to a wooden or plastic body they can be manufactured to any size.

Most household and nearly all chefs feel at home sharpening cutlery with sharpening steel, these work in the same way as a sharpening stone but are better designed to be used with kitchen cutlery.
Sharpening steels are also available as diamond sharpening steels.

These are the basics of sharpening an edge by hand, as technology has moved on machines have been invented to help simplify the process of sharpening an edge, these are varied and you can generally find a machine to sharpen most tools or a multi sharpener that will sharpen more than one type of tool.