"Wages" are payment for services you perform for your employer.
Wages include cash bonuses and commissions as well as vacation and severance pay. Tips are also considered to be wages if you receive at least $20 in cash a month.
Wages do not have to be cash. The cash value of any compensation paid to you in any form other than cash is also considered wages, (unless the form of payment is specifically not covered under the Social Security Act). Wages may include the value of things your employer provides like housing or a vehicle you can use anytime (instead of just during normal business hours).
Note: Reimbursement of business expenses and income you receive that is not based on work for an employer, like capital gains, investment income or lottery winnings, are not considered wages.