Computer software can be defined as a set of instructions that solve or perform a particular function in the computer. Other terms may refer to these instructions as algorithms. These algorithms or instructions can be grouped together to perform a specific task when this happens they are called applications.
In the simplest set of terms Computer software can be classified into two different types. These are System Applications and Computer Applications.

System Software

System software are basically software that are elated to the functioning of the computer. In cases of gadgets like smartphones and tablets, system applications are software that ensure they are functioning to the standard of the user. System software are normally written in a language that the machine can understand and are normally low level languages. They serve as an interface between the machines and the user.
Examples of System applications are the Operating System which controls the booting and shutting of the machine and also manage the hardware that are accessories of the machine.
System Software generally come already installed in the machine in question and are normally supplied by the manufacturers

Application Software

Application software are a set of computer software that are developed to provide a solution to a particular problem. They normally run dependent of the System Software. Examples of Application software include Microsoft Office. In this case the application software can work together to accomplish certain needs like the spreadsheet.
There are also user based application software which are developed by users to be able to accomplish needs of other users. An example would be an Accounting software developed specifically to meet the needs of the accounting department, a human resource software to meet the needs of the human resource department.
With the trend in technology, Application software are being integrated into one to be able to meet an entire organizations need. This means that the Accounting, human resources, Sales, Front Office software are integrated as one. This type of software is known as an Enterprise Resource Planning Software.

Conclusion

Computer software is the interface between the hardware and the user. It is not possible for hardware to work without the software installed. There is software in the market today that is able to accomplish nearly everything the human mind can think of, both free and at a fee depending on the developer and the function of the software.