"Software" is the term for a series of detailed instructions that tell a computer what tasks to perform and how to perform them. That includes all the routines and procedures the computer must follow to get the job done.
There are synonymous terms for "software." A "computer program," or just "program," is often used. Equally acceptable is the term "application" to describe the same set of problem-solving commands. Some examples of applications are word-processing software like Microsoft Word and spreadsheet software like Microsoft Excel.
Sometimes instructions are embedded in executable files, which have a .exe extension. Once people run them, these files launch a series of steps that tell a computer how to perform a given operation.