Which one [STRIKE]is[/STRIKE] refers to a host and [STRIKE]wihich[/STRIKE] which one [STRIKE]is[/STRIKE] refers to a guest ?
1. visiting a person
2. [STRIKE]vistied[/STRIKE] visited a person
Both phrases could refer to both a guest and the host although the only one mentioned is the host ("a person"). The first sentence uses the continuous and the second one uses the past tense. In order for them to be sentences you need more words and you need to say who the guest is.
1. The man is visiting a person. (The man is the guest. A person is the host. Present continuous.)
2. The man visited a person. (The man is the guest. A person is the host. Simple past.)