documentation of product requirements [closed]

How and by what method can we document the needs that come from various ways such as bugs and technical problems, or the needs that come from our users and customers? We also want to be able to identify the reason behind that case and the solution that has been implemented in that document, and we can, for example, refer to that document again a year later and find that problem reported and find the cause and solution.

We now use Terllo to document product features and technical team tasks. What is your solution to this problem?