When contributing to existing projects, look for and stick with the agreed branch naming convention. In open source projects this information is typically found in the contributing instructions, often in a file named CONTRIBUTING.md.
In the beginning of a new project the team agrees on the project conventions including the branch naming strategy.
Here's an example of a branch naming convention:
<user alias>/[feature/bug/hotfix]/<work item ID>_<title>
Which could translate to something as follows:
dickinson/feature/271_add_more_cowbell
The example above is just that - an example. The team can choose to omit or add parts. Choosing a branch convention can depend on the development model (e.g. trunk-based development), versioning model, tools used in managing source control, matter of taste etc. Focus on simplicity and unambiguity; a good branch naming strategy allows the team to understand the purpose and ownership of each branch in the repository.