Essentially these are extra programs that can be installed and used as part of a Browser i.e. they plug into it. Typically these would provide extra facilities like the ability to handle sound files or advanced graphics. What this means in practice is that, should a web page incorporate sound as well as text, the relevant plug-in will be needed before it can be read by any Browser and the sound played through the computer's own speakers.
Here the word 'relevant' means the matching plug-in to whatever piece of software was used to create that particular sound effect on the web page. Plug-ins come in sets of two; one is sold to the web designers to create a particular effect and the other is given away free to anyone with a Browser so they can see or hear that effect on their own computers.
Needless to say, this being the computer industry, there are a lot of plugins to choose from - and there is no such thing as compatibility. Every one of these special effects needs its own plug-in installed on the Browser. Some sites get around this by including a link to the plug-in manufacturer's home page where the relevant piece of software can be downloaded immediately, but, that apart, there is nothing else that can be done. Without the right plug-in the effect is unreadable.
It has to be said that some of these special effects can do wonders f6r a web page and really make it stand out from the crowd. It is even possible that some people will turn to that web page just to see it for themselves once the word spreads so there are good reasons for using them, naturally.
However, on the basis that the web designers will be more than ready to sing the praises of these things, perhaps it might be a better idea to concentrate on the down side.
First, and most obvious, is the fact that a special plug-in has to be installed on each individual Browser. As these are given away free that might not seem too much of a problem which would be a fair point if there were only one or two on the market. Unfortunately the number available is steadily increasing to the point where not even the most dedicated web surfer could hold them all. For those less dedicated, or still holding on to the notion that the computer is a business tool and the space on its hard drive should be reserved for business information, that applies even more so.
Also while these plug-ins are given away without charge it would be wrong to say there were no costs involved. All the manufacturers do is set up a website where anyone who wants it can download their particular merchandise - except the phone call might still have to be paid for. All of which explains why not everybody has even the most popular of plugins; they have better things to do with their on-line time and better ways of spending their money, especially as the size of these files means a long download. Stripped of its jargon that means waiting for what will seem like an eternity as some form of graphical display measures how much of that file has been received - and how much is still to come.
It therefore follows that plug-ins should be treated with caution. While they can greatly enhance a website, and in so doing greatly increase its value as a marketing tool, they do have their drawbacks as the extra cost of including them will be wasted if not everyone can read them. Because of this there can be no hard and fast rules about their use. Each case has to be judged entirely on its own merits which can only be done when a variety of factors are taken into consideration.
• How well known is it. An obscure plug-in will have very few users.
• How popular is it. All the manufacturers have statistics about the number of downloads from their site. These should be consulted when assessing the total number of people who will have that particular plug-in.
• How necessary is it. Is that particular effect so vital the site will be useless without it. If not why have it?
• Are there alternatives. Can a similar effect be achieved some other way either by using a more popular plug-in or by using more standardized methods.
• Who will see it. A highly technical, computer literate, user is more likely to have these plug-ins already installed. On the other hand a more general user might not even know what a plug-in is. That being the case consider who is likely to visit the website and take the decision accordingly.
Other than that there is very little advice that can be given. The situation is just too dynamic for even generalized rules quite apart from the fact that as each website and each plug-in are both in some way unique the number of permutations is, for all practical purposes, infinite.
That being the case ask the questions, take an informed decision – and then go on to consider the next piece of web software.