Definition
It is a description of your “perfect customer”. It is the most likely to buy and benefit from your product. It is defined by analyzing your current customer base and is used to focus your sales and marketing activities on the most likely buyers. In B2B, the definition is ambiguous: it may refer to both organizations and individuals. For this reason, I prefer using the terms Ideal Customer Organization Profile (ICOP) and Ideal Customer Persona Profile (ICPP), depending on the context.
Your ICP should be defined by analyzing your current customer base and the value you create for them.
It is used to focus your Go-to-Market strategy with tailored prospecting, messaging, and so on.