Full explanation
Burn rate is the speed at which your startup is spending more than it earns. It tells you how fast your bank account is shrinking.
Net burn is what really matters: monthly expenses minus monthly revenue. If you spend 5 000€ and make 2 000€, your net burn is 3 000€.
Controlling your burn is what gives you time to find product market fit. A high burn shortens your runway and forces panic decisions.
Concrete example
Your hosting, tools, and freelancer cost 4 000€ per month. Your revenue is 1 500€. Your burn rate is 2 500€ per month.