This software is made by Autodesk which is the company responsible for making AutoCAD which is an industry standard 3d modeling software. The 123D modeling tool was actually discontinued in 2017, but downloads still exist but are not supported by Autodesk. The tool is free to download and use and, for a free tool, is very powerful. This is a perfect software for an engineering or architectural student just breaching the world of 3d modeling and visualization. Many people that are familiar with Autodesk know Tinkard and Fusion 360. The Autodesk 123D software is between Tinkard and fusion 360 when it comes to tools and functionality. Tinkard, being browser-based has a lot fewer features than 123D or fusion 360. Conversely, fusion 360 is available for a cost (not a cheap one at that) but has the most functionality. 123D is a happy medium allowing for simple 3d designs for no cost. If you are a person used to the fusion 360 tools then you will probably feel very limited if trying out or switching to 123D, but don't let that be a deterrent. Evaluate whether you need the extra functionality, and if not, you may save yourself some money by switching to 123d.
In conclusion, if you are a student or starting a professional looking for a 3d modeling CAD software, Autodesk 123D is recommended. Due to the powerful, but the streamlined design of this software, it makes it a no brainer for anyone to just try out. Whether you are a professional, home DIYer, 3d printer owner or all of the more above Autodesk 123D is the choice for you. My advice would be to try out all 3 software mentioned and see which one you like better and if you can live with the cost of the extra functionality of fusion 360 carries with it.
The 2 key benefits are that it is free and that it is a powerful 3d modeling tool.