Tulsi is sacred in every home and worshipped in Hinduism
I am not Indian, I'm a Christian but I'll talk about the connection between Tulsi and Hindu.
Most Hindu families have tulsi or what they call holy basil in their house. It is typically a small plant, with green leaves, grown in a small pot or a stand specially designed for this purpose. In addition to watering the plant every day, many people will place an oil lamp next to it each evening. This practice is a daily ritual for many, but I wonder how many actually think anymore about the reasons for the practice.
When I lived with my parents, we used to have an Indian neighbor who would walk around the tulsi plant with an oil lamp at dusk. I always heard her say something while doing so that I still cannot remember clearly. One time, I asked her daughter what she was saying and she replied, it is said to purify the air, like for health reasons. I have not seen this claim verified in any literature though.
The religious connection between tulsi and Vishnu is very old, although I can't say for certain if it has been verified historically. Some people claim that tulsi is in fact an incarnation of one of the goddesses and that it is treated with the same kind of respect as any of the gods and goddesses. Plucking the leaves from the tulsi plant should be avoided unless it is done on a certain day, possibly Thursday or Tuesday.
What I find to be a bit confusing about tulsi is that it seems to be both ubiquitous and sacred at the same time, even though it is very common in many homes. No one seems to treat tulsi casually nor do they throw it away like most other plants. Even households that do not practice their religion in any formal way still typically have tulsi in their home.
Tulsi is treated differently than any other plant. I have no doubt about that. I don't know for sure whether all of the Hindu households truly understand the religious theology connected to tulsi or whether they merely continue following the custom because it has been passed down through generations.