Seva and Simran are the foundations of Sikhism. It is the duty of every Sikh to practise Naam Simran daily; the remembrance of the Almighty Creator and engage in Sewa - selfless service, whenever there is a opportunity - in Gurdwara (Sikh temple); in community centre; old people's homes; care centres; major world disasters, etc.... The Sikh holy scripture, Sri Guru Granth Sahib mentions the importances of these two qualities many times. On page 25, the SGGS tells us: "This body is softened with the Word of the Guru's Bani; you shall find peace, doing seva (selfless service)".
Simran ( ਸਿਮਰਨ ) refers to the remembrance of God by repetition or recital of His Name: Nām or of the Holy Text from the Two Granths of the Sikhs: the Sri Guru Granth Sahib and the Dasam Granth. The word is derived from Sanskrit word Smaran meaning Remembrance. Also translates to ‘Meditation’ – The verb Simar, which is derived from Simran means meditating.
Seva (also spelt ‘Sewa’) is a word used to refer to the practise of "selfless service", performed without any thought of reward or personal benefit. The person performing this service is called a Sevadar (service-doer). All Sikhs are encouraged by their Guru (Guru Granth Sahib) to perform Seva or Selfless Service. This is not only good for community relations but also is good for the moral uplifting of the person. You will find Sikhs engaged in free service in Gurdwaras, washing dishes or cleaning the floors, painting the walls, etc. Sikhs are also encouraged to help the community by performing unpaid work in hospitals, old peoples' homes, community centres, etc. For many people this activity forms an essential part of their life, providing spiritual fulfilment and practical benefits.
A Sikh needs to perform both these function in equal amounts. It is said by many Gurmukh folk that Seva and Simran are like the two wings of a bird. If one wing does not function, the bird cannot fly - meaning that the Sikh need to perform both these functions equally to elevate to a higher spiritual plane!