Importance of twelve names of Bhagwan Mahavishnu

Lord Vishnu has innumerable names. Out of these, Bhishma composed 1000 names and gave it to Yudhishthir, which became famous as Vishnusahasranama. From these 1000 names, sages selected 12 names which explain greatness of Lord Vishnu. In fact, these 12 names are chanted when one performs Achaman before starting any ritual, ensuring that they are chanted regularly.

1. Keshava – This has several meanings. Keshava means one who removes difficulties (klesha). It also means a person having curly hairs. According to Adi-Shankaracharya, the name Keshava was bestowed on Narayana by Lord Shiva.
2. Narayana – naranam ayanam - Nara means the universe of sentient and non-sentient beings. Ayana means one who is the support (adhar) for it. There is also other view - narah ayanam yasya sah - means one who is immanent in all, that is all that exists in the universe has Narayana as its support.
3. Madhava – “Ma” means Laxmi. "Dhava" means husband. Hence Madhava means husband of Laxmi (wealth and prosperity). As the husband of Laxmi, he possesses all wealth, knowledge etc.
4. Govinda – The word “Go” has several meanings in Sanskrit. It means the mother Earth or a Cow. So Govinda means He who saved mother Earth from Pralaya or He who is protector of cows. His simplicity is exhibited when he acts as a cowherd and protects people from Indra's deluge in his Krishna avatar.
5. Vishnu – It means, the person who is present in everything and everywhere i.e. the person who occupies both the Chit (possessing intelligence) and Achit (without intelligence)
6. Madhusudana – This denotes the person who has attained the control of Indriyas (sense organs) or the person who slayed the asura named Madhu. This aspect of the name is aptly explained in Bhagwat Geeta by the shloka “Paritranaya sadhunaam vinashaych dushkritaam”.
7. Trivikrama – This means a person who has conquered the world in three steps. This is also called as giant form of Vishnu's Vamana avatar when he restored kingdom of Indra which was being ruled by asura Mahabali.
8. Vamana – This was the stage before Lord Vishnu manifested as TriVikrama. Lord Vishnu transformed himself into a brahmin of 3 feet tall to beg Mahabali for the kingdom on behalf of Indra. In this way he exhibited his greatness i.e. he became a dwarf in order to help Indra, by lowering his stature in presence of all.
9. Shridhara – It means He is the lord of “Sri” (Laxmi) i.e. husband of Laxmi.
10. Hrishikesha – It means he makes the indriyas function according to his command.
11. Padmanabha – It means who has the Lotus (padma) in his naval (nabhi). The lotus on his naval is indicative of the fact that he was responsible for the creation of the universe
12. Damodara – When Mother Yashoda tied him by a rope on his waist, it left a mark on his stomach. Damodara means, He who has the mark of the rope. This act of His getting tied, shows that he will be the slave to all those who tie him with their love. 

All these 12 names are very sacred for the Vaishnavaits. In order to emphasize these 12 sacred qualities of Lord Vishnu, Vaishnava saints carry sacred marks on their body – 1 on forehead, 3 on stomach, 1 on left shoulder, 1 on chest, 1 on right shoulder, 3 on neck, 1 in back, 1 on the back side of neck. They recite above 12 names while applying these marks on their body.