Traditionally, a book tour is a physical tour across the country to numerous bookstores. Publishers used to pay for these and such tours typically included numerous radio and TV interviews, too. They still do these for some elite authors. Various bookstores, especially strong independents, have guest authors regularly, and there still is the occasional radio show out there that would be interested. Today, there are some intrepid authors who arrange their own physical book tours, and possibly you could arrange a podcast tour on your own, too.
Blog tours are what used to be a common practice pre-2016, when they dropped off dramatically. A company would arrange dates with a certain number of blogs, the author would provide content, and then the company would put that content on each of the blogs on the tour. Ideally, the author would also be available to answer questions on each blog on the date the post debuted, but otherwise the company handled the repetitive chores and setting everything up with the bloggers. Sometimes, prizes were involved.
Takeovers are when you put your content on someone's Facebook page, with their permission, and those usually involve offering prizes and doing interactive chatting with that person's followers.
I did numerous guest blog posts in 2015 and 2016 and I don't think it did anything but waste my time, but it is totally free if you arrange it yourself and it does get eyes on your book. There still are people with blogs who are eager for guest content. I suppose the presumption is that you tell your fans about the guest post and thus bring them to that blog and increase that blog's traffic, but in reality I suspect most people doing guest blogging are reusing content their followers may have already seen, or don't have any followers yet, or whatever. If you have the time, it can't hurt.
There used to be lots of book bloggers, people who would read and review your book and post their review on their blog and thus give you some important word of mouth. By 2014, when I was investigating them, they all were completely overwhelmed by the number of indie books submitted to them. I went through lists of hundreds of people and almost all said they weren't taking any new submissions. There still are a few book bloggers out there, though, if you search for them. Might be worth a try since usually it costs almost nothing. Some book bloggers wanted a physical copy of the book. It's an expense, and they probably would resell the book whether they reviewed it or not.
