Not all photographs come free online. There are some images which are used only for specific purposes and are to be used only in some occasions and throes are known to be stock images.

1. In today’s era of internet, creating a website has become a matter of few
minutes. But to run any website successfully, one cannot deny the necessity
of images in it. Images are like life to a website and without them, it would
be dull and boring and in most scenarios without an image the description
of the text becomes impossible and meaningless.
What is a stock image?
Not all photographs come free online. There are some images which are
used only for specific purposes and are to be used only in some occasions
and throes are known to be stock images. They are photographed by the
specialist photographers in that specific field and may contain information,
which is obtained by spending so much cost. For example if we take the
photographs of a particular remote and beautiful island, the cost incurred
in going to the place and staying there would not be zero and the
photographer has to spent considerable amount of time in zeroing the
perfect locations and has to take it with an SLR, and the whole process is
time and cost involved.

2. This time and cost is collected by the photographer in the form of selling
the photograph. These types of photos are called stock images.
Use of Stock images
With the advancement of World Wide Web, most of the stock images
selling companies have become online based. The stock images of today
are mostly royalty free, which means if once they are bought, they can be
used how many ever times a buyer wants to use. This has made purchasing
of stock images much cheaper and the entry of some online companies
like Imageselect also reduced the prices of stock images, by the methods
followed by them. They ask the amateur photographer to upload their
photographs for free and if the images get any buyer, they give the
photographers some sort of commission and these images are royalty free.
It is a win-win move to photographers as well as the customers.
Reasons to take stock images:
Now days, stock images have effectively replaced traditional photography.
There are plenty of reasons proving this.

3. Saves time that is a major constraint in big photo shoots
Buying images online is an effective way of saving time. Conducting photo shoots
demand loads of time investment which is not possible in most of situations. The
images available on web are near to perfect and can be bought in few minutes.
Sometime, even after investing so much time, outputs are not as per what was desired
so Micro-stock photography plays a vital role.
Wide variety of images
Websites are full of diverse images for the people to choose from. People have range
of options and can even make use of filters to pick the right images from pool of
images available online.
Get copyrights and images both easily
People can buy images and their copyrights to prevent the use of the photo by any
other business commercially. This is cheaper than investing money on a photo shoot.
The photo then becomes the stuff of the company or individual owning it exclusive
rights.
Affordable than photo shoots:
Stock images are cost effective and royalty free. Individuals, companies can buy the
photos easily at much cheaper rates than conducting big shoots.

4. That amount can be used for some other work to promote businesses and websites.
These are the reasons of people resorting towards low cost stock images. Hence,low
cost stock images are reality on web and are being used by businesses, individual and
site owners effectively.
Article Resource: http://stockphotogalleries.wordpress.com/2014/02/01/low-coststock-images-a-reality-on-the-web/