To illustrate, let's consider a company that buys a $100 data centre every 10 years. (To keep things simple, let's assume the data centre is worthless after 10 years.) The data centre generates $20 in revenues for each of those 10 years.
Instead of showing an $80 loss in year 1 and then a $20 profit in years 2 through 10 (with the expectation of another $80 loss in year 11), accountants smooth the numbers based on expectations. The $100 data centre cost is "depreciated" over the expected lifetime of the asset. So one might account $10 of the data centre's cost to each of its ten years, thereby producing $10 of profit each year. This better reflects economic reality.
Ebitda does not include depreciation. The aforementioned company's Ebitda would be $20 for years 2 through 10. This is a small problem in year 2. But if you're an investor in year 10, ignoring that depreciation is the flip side of capital expenditure, you're in for a nasty shock when year 11's predictable capital expenditure comes down the line.