There are a few things you need to know in order to understand how projects work in Jira. A "project" in Jira is simply a container for issues. An issue is a piece of work that needs to be done. It could be a bug that needs to be fixed, or a task that needs to be completed.
Each project has a unique identifier, which is used to identify the project in Jira. The identifier is used in the URL for the project, and is also used to identify the project in the command-line interface.
Projects can be organized in any way that you want. You can create as many projects as you want, and each project can contain as many issues as you want.
You can also configure how projects work in Jira. For example, you can specify who has access to a project, and what permissions they have. You can also set up email notifications for a project, so that people are notified when an issue is updated.
If you're new to Jira, it's probably best to start with a simple project. You can always add more projects later, as you become more familiar with how Jira works.