Distributions from a regular 401K are taxable as ordinary income. Normally 20% of your distributions will be withheld for federal taxes. The IRS assesses an additional 10% early withdrawal tax on distributions taken before age 59 1/2, unless you qualify for one of the exceptions. You will receive a Form 1099-R at year's end giving you the specific dollar amounts. Here's what the form looks like: https://www.irs.gov/pub/irs-pdf/f1099r.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.