The rent you receive is taxable income, but before taxes are calculated, all your expenses have to be subtracted. (You're not considered self-employed, so there is no SE tax.)
Expenses are stuff that you have to spend just to keep things going. That is, insurance, repairs, lawn mowing, painting, property taxes, mortgage interest and the like. Those are all deductible.
Other things, like new appliances, improvements, and the building itself, are depreciable assets. Those are assigned a time period (from an IRS chart) over which you divide the deduction expenses. A rental house is 27.5 years; a commercial building is 39 years. Other things are less. Often depreciation means that you will have a tax loss, even when your cash flow is positive. Be aware that the tax is only being postponed, not eliminated.
When you sell the property, the depreciation is subtracted from your purchase price to come up with "basis for sale," which will increase the amount of tax you pay at that time.