Does it imply that they are likely to accept me or are unsure of accepting me? I thought that my application essay was lacking yet they emailed me and said they wanted to give me an interview. Schools don’t offer interviews to every student so I’d like to know what this means if I was given one.
Based on your application you were not rejected. 
If they were going to reject you for sure, they probably wouldn’t offer you an interview. They are at least considering you. Interviews don’t usually hold a lot of weight, so don’t stress about it too much. You will be having a conversation, and they won’t be grilling you. Do think of a couple of things you’d like to bring into the conversation if you can. Look at the website, or the school’s Wikipedia entry, and think of a couple of things to ask about the school. You can ask the interviewer why he/she chose the school.
It means the school interviews and had an interviewer available.
Yes, I suppose it means you made it past first cut, but there are still miles to go before decisions. Take the interview and do your best. Unless this school only offers “informational” meets, whether or not it matters, there will be a report generated and adcoms will read it for insights.
It means that if you are interested in this place, you need to accept the interview offer, and go to the interview.
It means you applied.to.the college and they have available interviewers in your area. I would not read anything into it. If you are interested.in the school then take the interview.
My daughter got interview from Cornell. The interviewer took note during the interview. It might mean something.