A means of doing something is a method, instrument, or process which can be used to do it. Means is both the singular and the plural form for this use.
You can refer to the money that someone has as their means .
If someone is living beyond their means, they are spending more money than they can afford. If someone is living within their means, they are not spending more money than they can afford.
If you do something by means of a particular method, instrument, or process, you do it using that method, instrument, or process.
You can say 'by all means' to tell someone that you are very willing to allow them to do something.
You use expressions such as 'by no means', 'not by any means', and 'by no manner of means' to emphasize that something is not true.
If you say that something is a means to an end, you mean that it helps you to achieve what you want, although it may not be enjoyable or important itself.