Mark yourself as "Willing to travel" if you are generally willing to do so in relation to your job. Some clients might require freelancers to work fully or partly on-site. This might include requests to relocate to a specific city or visit the on-site team for a limited period of time - a few days every week or month, during the project onboarding, during important milestones, etc.
This information is only used to match you with potential jobs. Any travel details should be negotiated directly with your client.