Definition - What does Software Metric mean?
Software metrics are measures of the success of a software process. In theory, metrics can help to improve the development process and provide companies with information that makes future projects more predictable, efficient, etc.
Techopedia explains Software Metric
Measuring what is "good" when it comes to software is very difficult. Ideally, a metric is quantitative, but so much is subjective, that it is difficult to be completely this way. For example, you could measure a programmer's efficiency by the number of lines of code he/she produces in a day. Looking at sheer volume completely ignores quality of work. More code isn't better. Often, more code is in fact a negative if the problem can be solved more elegantly.