Nice, concise answer. I just want to emphasize that the practical consequence for most taxpayers is that "expenses" are generally currently deductible in full on the annual tax return, as opposed to having to be spread over future tax years ("capitalized") - normally not as advantageous.

Please note that my answer and/or comments do not constitute legal advice and may not be relied upon for that any purpose - please consult a tax professional to address your specific situation!