What is MTL anyway? I'm kinda confuse...
Machine TransLated. The original (probably) Japanese text has been translated into 'English' via means of an auto-translate program, whether it's from Google, Translator++ or the like.
This means the Engrish will be decently readable but grammatically poor at best, and absolutely hilarious and/or near incomprehensible at worst. There is usually minimal translation effort done on the part of the uploader; most will go to the extent of word-wrapping the text so it fits within the textbox, and no further.
You will likely have a difficult time understanding the plot unless you take the time and effort to decipher the lines. This can be alleviated
a little if you have a rudimentary understanding of Jap / Mandarin sentence structure, but it'll still take some work. Not exactly the best idea for a good beat-meat time.
TL;DR: MTL = Machine TransLated - translated by a program, not by a human.
P.S: I apologise if the tone of this post sounds like it's ragging on uploaders. I'm
not doing that at all in the slightest. It's tough and time-consuming work to translate, and I appreciate the efforts of the uploaders for helping in their own way to make things at least partially understandable from moonrunes, which a large majority of us can't even begin to read. I stated that understanding Jap / Mandarin structure helps because I have studied Mandarin from young, and can understand
very rudimentary Jap, and I'm confident in saying that having this knowledge
does help. It does take more brain power than I'm usually willing to give when I'm having some good old self-contact though.