Profile, in a generic sense as a verb, means to describe, and that is what actually Bluetooth Low Energy Profiles are. In a nutshell, A Bluetooth Low Energy Profile is a description of the behavior of a Bluetooth Low Energy device, and it is also an answer to questions like "What is the purpose of this device?" or "What can this device do?"
Perhaps, a conversation between a company executive and the software development team lead revolving around a Bluetooth Low Energy device will give you an idea of the importance of profiles for Bluetooth Low Energy devices:
Healthcare Company Executive: "We want to roll out a new series of health devices for recording and monitoring a user's blood pressure"
Software Development Lead: "Ok, sure. ...