Visualization is any technique for creating images, diagrams, or animations to communicate a message. Why visualization is very important is due to the fact that it communicates more information, more effectively.
Like Visualization, Data visualization is technique for creating visual elements like charts, graphs,maps etc using data. In simple terms its graphical representation of information and data. Each of these visual elements like charts, graphs, maps etc tells a story with purpose in nutshell.
To explain better lets consider an example where a sales manager is given an excel sheet with sales details of all sales done by sales person working under him. He may have to sit for hours trying to figure out the performance of each region, each sales person, comparing performance with previous months etc. But with data visualization technique all these data could be represented visually in form of graphs or charts which will give the sale manager all the information he/she needs within minutes, based on which the sale manager could take appropriate decisions or develop strategies.
Large data could be analyzed and visualized easily using data visualization tools/software. A Data visualization tool/software allows the user to select the best way of presenting the data with ease. Depending on what user feel is best, user can choose between pie charts, bar charts, line graphs etc to express the data better.
5. Knowage (Open Source)