Software as a service (or SaaS) is a way of delivering applications over the Internet—as a service. Instead of installing and maintaining software, you simply access it via the Internet, freeing yourself from complex software and hardware management. SaaS eliminates the need for buying software which becomes outdated, or require the user to apply updates. Everything is handled from the server side or “cloud”.Some more well known examples of SaaS products are the Adobe CC suite of products (Photoshop, Lightroom, Illustrator, etc.), Salesforce, Netsuite,  and many of Microsoft’s products including Office (Excel, Word, PowerPoint, etc.)
andreessen-post The following is an excellent article published on the Andreesen  Horowitz website:

Tune into any cable network stock market channel and the airwaves resonate with one consistent theme: SaaS companies are simply too expensive. In fact, we might even be in a bubble!

The argument goes as follows — high revenue growth coupled with lack of profits means these businesses are fundamentally broken. Just as we saw in 1999-2000, investors’ willingness to pay for growth at any cost will end and many SaaS companies will be left behind. [Click here for the full article…]