There are Sikhs by belief and Sikhs by birth. A Sikh’s belief is defined in article one of the Sikh Rahit Maryada (Code of Conduct). However, there are people who would identify themselves as Sikhs but who may not believe in the religion. It was in recognition of this distinction that Sikhs successfully lobbied for paragraph 67 of the 2001 UN Declaration against Racism which takes note of the multiple bases of identity.
Within mainstream Sikhi there is the unifying belief in the Guru Granth Sahib and the Guru Khalsa Panth (Khalsa). Variant groups that exist are the Namdharis and the Nirankaris who believe in a living human Guru. These groups number around ten thousand out of a global population between 25 and 30 million.
Within the community there are different attitudes towards the Khalsa. Some Sikhs regard it as the ideal as it involves following in the footsteps of Guru Gobind Singh. Others regard the Khalsa as an ideal but decide that the commitment is too great.
Within the Khalsa itself there are those, belonging to the Tat Khalsa, who take seriously the responsibility of the Khalsa to update the Rahit Maryada (code of conduct) so that it is relevant to changing circumstances. This was last completed in 1945. However, others differ and follow what they regard as a more traditional line (for example, the Akhand Keertanee Jatha and Damdami Taksal). It is important to note that while they might regard the Tat Khalsa as overly lax, from the Tat Khalsa perspective there is nothing wrong in following a more traditional approach. Their argument is that the stricter or more particular approach cannot be applied to people who do not agree with it.
Another difference is between the Khalsa who follow the code of conduct agreed in 1945 or particular practices followed before then and those who follow Sants, living saints. The followers of a Sant may argue that the particular religious experience of a holy man is better able to guide their practice than historical or consensual codes.