Boot camp is an American term for a series of sessions at a remote location where you are drilled in certain knowledge and skills that are necessary for whatever occupation you may be involved in. It used to apply to military purposes, but used as CCNA boot camp, it refers to people eager to learn about CCNA to go to a certain place so they can be drilled in what they ought to know about CCNA and how to apply what they learned in real-world situations.
You may like to call these CCNA boot camp sessions as seminars or conferences, but due to the difficulty of living up to the CCNA certification standards, the sessions may actually be quite intense learning experiences – hence, the nickname boot camp.
But a stay at the CCNA boot camp does not come cheap. They may require you to submit proof of prerequisites like: being employed for an IT employer who will really need your knowledge and skills in CCNA; capacity to pay (meaning, who will be paying for this – you or your employer?); and then the payment itself which should cover your daily board and lodging for the duration of the boot camp sessions, the tuition for the training and the materials, and perhaps some miscellaneous expenses.
What is the benefit of staying at CCNA boot camp? First, you get to really immerse yourself in the field of CCNA training knowledge so that you become better at this field, if not an actual expert. Second, you get to interact with people who may be much better than you at CCNA and learn from their experience and any insights they may share with you. And third, even if you leave your present employer, your employment chances are radically improved because you carry your skills with you even to the next employer.