The title is deceptively simple: it lets us know that the poem is about a tiger. So, we expect it to be just that, about a tiger. However, as we start reading, it becomes clear pretty quickly that this isn’t just any tiger. It probably isn't even a tiger like you’d find in a zoo. It could be a symbol Blake uses to make a far deeper point than something like "Tigers are scary."
It should be said right up front: don’t freak out if you don’t know what the heck is up with this whole tiger business. What does it mean? Why a tiger? Why is it "burning"? Relax, the tiger is the central mystery of a poem about mysteriousness – it’s a device – and scholars have been debating about it for 200 years. As with all of Blake's poems, and perhaps all good poets, don't jump to conclusions. Keep an open mind and let Blake show you a new way to think about it. Is it about a tiger? Yes, but only as much as Moby Dick is about an albino sperm whale.