What is a backlog?

A backlog is a visible list of (often prioritized) uncompleted work items (deliverables), or drivers that need to be addressed (source: https://sociocracy30.org/guide/glossary)

Many teams use Microsoft Excel to create a backlog. Tools like Asana, Microsoft Teams, Jira, Trello, etc. are better for managing day-to-day tasks in a team. It is a best practice to discuss (with the product owner) how to implement this in a team. Put this on the backlog. And what about issues? Also think about a process to manage issues. See issue management for more info.