OTT stands for Over-The-Top. As such, OTT services refer to services that you use OVER your mobile network operator. The network operator functions as a pipe for delivering OTT services to users. As such, any service you are receiving over the Internet that is NOT provided directly by your mobile network operator or Internet Service Provider (ISP) is OTT. Are you seeing where this is going? Because they are not the direct providers, they do not get paid for it besides what you pay for internet access.
So, OTT includes delivery of video, audio, instant messaging and the like. Skype is OTT. While it uses your network provider’s internet service for delivery, it is not provided directly by them, but by someone else, Microsoft in this case. Mobile network operators are already losing revenue to OTT voice and messaging services in particular. When you make a Skype call, the operator loses voice revenue to Skype. A lot of voice and SMS revenue has been lost to messaging services like BBM, WhatsApp, Skype, Viber and others too. Bad business for network operators.
In recent times, some operators have been up in arms to attempt to block some OTT services. That is a dumb and retrogressive idea, in my opinion. Like everyone else has had to adapt to the realities of the new connected world, network operators need to adapt too and not truncate progress. They can become more efficient data pipes, so they are the preferred network of choice for subscribers looking for data services. They can also choose to get into the OTT services business. For example, MTN getting into DoBox is an example.
Anyway, now you are not so lost when you hear some techie person use the word OTT. You at least have an idea of what he or she is talking about. Thank me later.