Here's a typical post from a newcomer on this forum

Newcomer: "Hi here's a bunch of stats about me, please evaluate my chances and tell me where to apply."

"Senior" Member: "Generic advice and insights about profile, you should target T50 (T20, T10 etc...)"

Newcomer: "Wow here are some platitudes for you. When you say I should focus on T50, what specific schools are you talking about?"

"Senior" Member: "There aren't any specific ranking systems that are used. It's really up to you, so your top 10 probably aren't someone else's. Good luck!"

Newcomer then leaves and never spends time in our little community ever again.

So I'm going to give some guidelines as to what I am referring to when I say T50 (T20, T10 etc...). The thing is that we don't like listing specific schools people should apply to. A big reason for that is we don't know your specific interests. We can't tell you specific professors at specific schools because we don't know exactly what you want to do (and if we do know specifically which areas, we don't want to be liable for you not getting into any programs).

That being said we are quick to list which tier of school you should focus on. Tier of school is exactly what we are talking about. So here is my advice and guidelines for tiers.

1. T10 - Everyone on the planet knows these schools names and knows what they focus on. If you are wondering if your great aunt Sally will know what school you go to when you tell her about your program at Christmas, the school is not in the top 10.

2. T25 - These are your bread and butter schools. Sure they don't have quite the same name recognition as the top 10, but anyone who knows anything about your area of research will probably know someone at these schools. Tenured profs are published in top journals for your area. Uncle Tim will at least know the school for their athletic programs.

3. T50 - Now we're starting to get into your second significant other territory. Let me explain. Your first boy/girlfriend was great. They did cute stuff for you, you held hands awkwardly and you were so happy to tell your friends all about her/him. Then you broke up. It was hard, you spent some time getting to know yourself (not too much time, though, you were probably in high school). Then along came X. They were a little rough around the edges, and you weren't quite as keen on bringing them over to your parents house for dinner as your first, but they had some good characteristics. Maybe they're really cute, or maybe they always remember your birthday, maybe they have one extremely research active faculty you'd kill to work with. Here's my point, these schools all have good things about them, but they can be rough around the edges. You'll probably only have 1 or 2 faculty you'd love to work with, but you can still put out some amazing research and come out with a good job afterwards.

4. T100 - These schools aren't known for their research output. Their professors are probably teaching a hefty load while they are making time for you as a PhD student. That's not to say they aren't good, but it will be harder to find a job at a top program afterwards. If you know this going in, though, that's not a big deal. They're still accredited and that means you should be able to get a job afterwards, it just might be more teaching focused. There are plenty of good reasons to go to these schools, though, and I'd be more than happy to discuss with any of you the merits of these programs.

5. T500 - Since most fields don't have more than 100 accredited PhD programs available these programs are probably non-accredited. I don't have a lot to say about them. I wouldn't apply to them, but that doesn't mean you shouldn't. Perhaps there are extenuating circumstances that preclude you from applying to top schools. If a PhD is your dream and this is your only opportunity don't let anyone (ESPECIALLY ALL OF US!) keep you from applying or going there. We all have deeply personal and private reasons for doing what we do. Do what you must.

The only other advice I would give is to never, ever pay for a PhD. If a school isn't going to offer you funding, keep on looking. Professors don't make enough money to cover the huge loans you would require to pay for life.

That is my take on school rankings and the jargon used on this site. If you are a member and have suggested someone apply to a T50 (T20, T10 etc...) program and disagree with what I have said, please chime in. I think that this could be a useful place for applicants to look when we intentionally vaguely tell them what tier they should consider.