Hi
barnaeva just a recently accepted applicant, but thought I'd chime in to help. The MBA process is intense and there is a lot of info with a lot of nuances but will try to share some general information. The threads you are seeing that say 2020 are for people applying to be in the class of 2020, which refers to their graduating year. So for most people applying to a common two-year program right now they will start this fall if accepted and graduate in spring 2020. People starting in the fall of 2020 will be the graduating class of 2022. There are also one-year MBA programs that might go summer 2018 until summer 2019 or I have seen some starting in January (and I am assuming go until the next January). There also are some schools where you start in January and do about 1 1/2 years of school because you don't do a summer internship and instead take classes during the summer. Columbia University has a program like this as an example (pretty sure there are others but didn't look into this particular program myself). Generally one-year programs are for people with more business experience or perhaps more business education (so they can take accelerated courses) and then usually both one-year programs and programs without internships are for people who don't want to switch industries and likely just climb the ladder faster since internships often help people to transition to different industries and generally much different roles.
In terms of if you apply right now yes you'll generally be applying to start this year in fall 2018 (I believe some schools like INSEAD 1-year program that starts in January and the Columbia program January program I mentioned will be accepting applications for January 2019 soon though). However a lot of schools' first couple deadlines have passed and the chances of acceptances start to get a lot harder in later rounds. Do you have target schools in mind? If so I would check their websites for their deadlines. Schools with three deadlines accept most students in Round 1 and Round 2 (most of which have passed). Schools with more rounds by probably Round 4 or 5 is when a lot the class is already accepted in earlier rounds and it will be more competitive for you.
If you do not have target schools in mind- have you taken the GMAT/GRE? You said you are just starting out in the process. If you haven't taken the GMAT/GRE it would be very hard to apply this year and start in the fall. The GMAT and GRE takes a lot of dedication to study for and get a good score to go to a school that will be worth the cost and time. Most schools last rounds are in 2-3 months at the latest and that is pushing it to have enough time to study for a test and then apply. If you haven't taken a test yet I would determine which test you'll take (GMAT is most common, but if you determine you'll do far better on the GRE and all schools you are interested in accept the GRE it might be the right test for you). You want to shoot for getting a GMAT/GRE score above your target schools' averages. Then you want to spend a lot of time researching the schools you want to apply (some research while studying for the GMAT/GRE and then a lot of research after when you are working to write your essays). This takes a lot of time so if you're just starting now you'll likely be looking to apply the next Round 1 (this fall 2018) to start school in fall 2019. Round 1 you'll have a much better chance and depending on your background (Indian IT male, Asian male, white male, banker/consultant) can help a little bit or can even help a lot.
Even if you have taken the GMAT/GRE already it still might be tough to apply this year if you don't have any target schools. Generally putting together a great application takes time to learn about a school and write essays that show why you are a good fit. Not impossible, but difficult to do if you're just starting school research now and trying to apply in the next month or two. And again later rounds are really competitive because there are fewer spots.
Hope this helps. I would encourage you to go through a lot of the forums and read more. Posts towards the top of each forum usually have a lot of helpful information. If you haven't taken the GMAT go to the General GMAT question forum and look for posts at the top that talk about plans and preparing. There also is this post here with a comprehensive guide from GMAT Club about the application process (for after you have a GMAT score, but encourage to read it even when studying for a test)-
https://gmatclub.com/forum/new-gmat-clu ... 23494.html I haven't personally used it since I got my info from all different sources over time, but this forum in general has tons of great info and I imagine it compiles a lot of info together in one place.
Edit: saw you share a bit about your profile on another post. Yeah with you not taking the GMAT yet I would highly encourage you to plan on applying in fall 2018 to start in fall 2019. Especially with your lower GPA it will be very important to rock the GMAT (which will take time) and then apply in Round 1 when the class is empty. Applying now in later rounds you'll have a big weakness (GPA) even if you crush the GMAT in like the next month and can turn around a strong app (essays, recommendations, etc.) right after. That can be tough. Places like Ross are especially competitive and even Indiana and USC I imagine are competitive last round. Doing Round 1 you'll have plenty of time to study for the GMAT (and possibly retake if you need to), you can visit the schools you are interested in if possible and attend their webinars and maybe an MBA fair in your city and demonstrate your interest. Plus you'll have a bit more work experience (a bit under the average right now for many schools) and show longer volunteering experience.