Short Version: If you are married filing jointly, your social security is taxable above $32,000. If you are single the number is $25,000. Those income amounts would include the usual, (wages, pensions, business income, etc.), PLUS 1/2 your social security.
Here's the worksheet link: http://www.irs.gov/pub/irs-pdf/n703.pdf
Short Version: If you are full retirement age (66 right now), nothing happens to your social security, and the above rules apply on taxability. If you started receiving social security before full retirement age, then your social security will be reduced by $1 for every $2 for the amount you earn over $17.040 in 2018.
Here's an informative link: http://www.cbsnews.com/news/can-you-work-while-collecting-social-security-benefits/