I use Canon EOS 600D and I want a lens with a larger range. I found out Tamron 16-300 f/3.5-6.3 Di II VC PZD Macro Lens, I added it into my wishlist. I did some research on it and I'm scared that it couldn't fit to my Canon EOS 600D. I'm still a beginner... I'm confused with EF, EF-S and APS-C/DX. Can someone please explain it to me?
Yes. Just make sure that you buy the Canon mount version for this lens, as third party lens makers generally also make versions with mounts for Nikon and other camera brands.
The EF or EF-s version of this lens will work on your camera, or any ASP-C Canon EOS DSLR, or the EOS M, with a separate adapter (the EF-s to EF-m adapter). The lens will be able to be attached to other Canon DSLRs (i.e. 1D, 5D, or 6D) but extreme vignetting (i.e. very dark corners of the image, possible extending a significant distance into the image) will occur due to a reduced image circle size.
For information on the letters please see this question