Let's find out...
Out of curiosity, I have personally searched what is coaching via a search engine in the internet and found more than 2 billion results!!! Quite a few of them are from various coaching associations; some others from fellow coaches, who offer their services; etc.
Although I can relate in more than one way with some of the definitions that I have read, for me the most important definition, is the one from my clients. For them, Coaching is:
a reflective process in which the Coach supports them to close the gap between where they are and where they want to be
Coaching only adds value when it really helps the clients. Since my main goal is to serve my clients in the best possible way, this definition is surely the one that matters the most to me.
In case you are curious, here is some jargon that it is often used when reading about Coaching:
Coachee is another term that defines the client of a coaching process.
A client of a coaching process can be an individual or an organisation. Typically, when organisations finance the coaching processes of their employes, in coaching language the organisation becomes the Sponsor. The team or the person that receives the coaching remains the client or coachee.