Inkscape is a free and open source vector drawing app for Windows, MacOS & Linux, available for download free under the GPLv3+ license. The tools aims to support illustrators, designers, web designers or anyone wanting to create vector graphics.
It is hard for me to say when Inkscape would not be a good fit because of my use. I have referred people to those who provide promotional products as well as those who need to utilize their artwork and have it converted to a format such as Inkscape.
Adobe Illustrator is also used in our company sometimes however, Inkscape is used most considering the fact that it is completely free while Adobe Illustrator has to be bought through monthly/annual subscriptions that are expensive. For that reason we always opt for Inkscape. Not only is it a free software, but it includes almost all the features and tools that Adobe Illustrator offers, even though there might be some tools missing here and there, for businesses whose main focus isn't graphic design, Inkscape is the way to go. However if Graphic design or illustration is the only or the main factor of your business, I would suggest going for the investment and getting Adobe Illustrator.