Overleaf it is a collaborative web service for writing and publishing academic writings based on LaTeX and is especially design for this purpose. I think nowadays is the most used software for publishing in academics. The website describes its mission very clearly:
Overleaf is a collaborative writing and publishing system that makes the whole process of producing academic papers much quicker for both
authors and publishers.
Overleaf is a free service that lets you create, edit and share your
scientific ideas easily online using LaTeX, a comprehensive and
powerful tool for scientific writing.
Writelatex Limited, the company behind Overleaf, was founded by John
Hammersley and John Lees-Miller, two mathematicians who worked
together on the pioneering Ultra PRT Project and who were inspired by
their own experiences in academia to create a better solution for
collaborative scientific writing.
Overleaf is supported by Digital Science. Digital Science is a
technology company serving the needs of scientific research. Their
mission is to provide software that makes research simpler, so there’s
more time for discovery.
From Tex to Overleaf: a not so short history
I think is important to have a look at the history of the technologies that are used by overleaf to see that they are designed by academics and used by academics. The history is basically an encapsulation of powerful complex technologies in a more user-friendly platform.
TeX is the core technology it was designed by Donald Knuth who was a professor at Stanford University this is an excerpt from this site:
As it turned out, TeX was
still a lot closer to a research project than to an industrial
strength product, but there were certain attractive features:
it was intended to be used directly by authors (and their secretaries)
who are the ones who really know what they are writing about; it came
from an academic source, and was intended to be available for no
LaTeX was set of macro to make TeX more accessible it was actually created at SRI International (SRI) an American nonprofit research institute by Leslie Lamport here an excerpt form an interview:
When Don was creating TEX80(?), the second version of TEX, the popular
macro package at the time was one written by Max Diaz I've forgotten
its name. I was in the process of starting to write a book, and I
found Diaz's macros inadequate. So, I needed to write a set of macros
for the book. I gured that, with a little extra eort, I could make a
macro package that could be used by other people as well. That was the
origin of LATEX.
Then it comes Overleaf so all these technologies are now on a server with ready-to-use templates from the most popular publishing companies and conferences.