Umrah is a mini Hajj that can be performed at any time of the year. It can be performed along with Hajj and in other days as well. According to Quran:

"---accomplish Hajj and Umrah to please Allah". (Al-Baqrah,1996)

In Arabic the word 'Umrah is derived from al-i'timar which means a visit. Here it means paying a visit to Ka'bah, performing tawaf around it, walking between Safa and Marwah seven times, and then shaving one's head or cutting one's hair short. There is consensus among scholars that it is a prescribed worship.

Ibn 'Abbas reported that the Prophet (peace be upon him) said, "An 'Umrah in the month of Ramadan is equal (in reward) to performing a Hajj.''

The Holy Prophet (peace be upon him) has described the great merits of performing Umrah.

He has said:

"The people who come to perform Hajj or Umrah are the guests of Allah because they visit His House on His Call; therefore, Allah grants them what they ask for".1

He has also said:

"One Umrah becomes an atonement for the sins committed up to the next Umrah".2

He has said again:

"Anyone who leaves his house with the intention of performing Hajj or Umrah and dies on the way will enter paradise without judgement. Allah is proud of those who perform tawaf of Baitullah".3

Performing Umrah during Ramadan is most commendable and equal to Hajj in merit and excellence.4

Clarification: It is quite true that an Umrah in Ramadan equals a Hajj and one can get the same rewards that are granted to one who performs a Hajj. But this act does not substitute the performance of Hajj which is Fard (imperative), once in a life time if one is financially and physically capable.