Assuming you are referring to when it is safe to hike in unfamiliar terrain:
Generally speaking, it is safest to hike in familiar territory. This way, you know the lay of the land and can more easily avoid any potential hazards. However, there may be times when you find yourself in unfamiliar territory. In these cases, take extra care to assess the situation before setting out.
If possible, try to get a map of the area or talk to someone who is familiar with it. Pay attention to your surroundings and look for any potential dangers such as steep drop-offs or loose rocks. If possible, stick to well-worn trails and avoid going off-track. And always let someone know where you are going and when you expect to return.
By taking these precautions, you can help ensure a safe and enjoyable hike no matter where your travels take you.