Distributions
IRA distribution rules are based on your age, and for Roth IRAs, on the length of time you have held your account.

Traditional IRA
The Traditional IRA distribution rules are based on your age, not on how long you have held your account.
The Traditional IRA distribution rules are categorized into three phases based on age:

        Premature distributions taken prior to age 59½
       
No-penalty distributions taken age 59½ and older
       
Required minimum distributions taken age 70½ and older

Premature distributions, younger than 59½
Distributions that occur before the IRA owner reaches the age of 59½ are subject to a 10% early withdrawal penalty, in addition to any income tax. The IRS waives this early distribution penalty when distributions are used for the following reasons:

        By your beneficiaries, at death
       
If you become disabled
       
If the money is used to pay qualifying medical expenses
       
If you are unemployed, to pay the costs of health insurance
       
If the money is withdrawn to pay for higher education costs for you, your spouse, children or grandchildren
       
If you use the money for the first-time purchase of a home for yourself
       
At any age, under what is known as the Substantially Equal Periodic Payments (SEPP) exception.

Normal distributions, age 59½ and older
Distributions that occur on or after the IRA owner reaches age 59½ may be subject to income tax but are not subjected to any early-distribution penalty.
Required Minimum Distributions, age 70½ and older
Once you reach 70½, you'll have to take at least a minimum withdrawal from your IRA each year. Distributions must begin starting April 1 the year after you turn 70½. If you fail to take distributions by that time, you will be taxed at a 50% rate on the amount that should have been withdrawn.

       
Learn more about RMDs

Roth IRA
The Roth IRA distribution rules are based on how long you have held your account and on meeting a qualified life event.
A Roth IRA has significant differences from the Traditional IRA:

        Contributions (though not earnings) can be withdrawn at any time without income-tax consequences
       
Penalty-free distributions are completely income-tax free. Penalized withdrawals of earnings are subject to the 10% early withdrawal penalty, plus income tax

Penalty-free distributions
To withdraw earnings without penalty from a Roth IRA, the funds must have remained in the IRA a minimum of five years AND at least one of the following criteria is met:

        You are age 59½ or older
       
You are disabled
       
The distribution is made to your beneficiaries after death
       
You use the money for a first home purchase; up to $10,000 lifetime