Guru Nanak’s philosophy consists of three basic elements: a leading charismatic personality (the Guru), ideology (Shabad) and Organization (Sangat).
He repudiated idol worship and did not favour pilgrimage nor accept the theory of incarnation.
He condemned formalism and ritualism.
He laid emphasis on having a true Guru for revelation.
He advised people to follow the principles of conduct and worship: sach (truth), halal (lawful earning), khair (wishing well of others), niyat (right intention) and service to the lord.
He denounced the caste system.
He laid stress on concepts of justice, righteousness and liberty.
His verses mainly consist of two basic concepts, Sach (truth) and Nam (name).
He introduced the concept of Langar (a community kitchen).
It was only towards the end of the 17th century that Guru Gobind Singh reasserted the idea of equality.
In 1699 Guru Gobind Singh attempted to resolve the differences among the various Sikh groups and created the Khalsa.
To create a sense of unity among the Sikhs the Guru started some practices which were to be followed by Sikhs.
These were initiation through the baptism of the double edged sword, wearing uncut hair, carrying arms, adopting the epithet Singh as part of the name.
The idea of Guru Panth was another institutional idea that emerged during this period.
It sanctified the collective authority of the Khalsa Panth, which equated the Panth with the Guru.
Guru Nanak in his last days had nominated a successor and paid homage to him, this gave rise to the idea that the Guru and the Sikh were interchangeable.
When Guru Gobind Singh created the Khalsa he chose the panj piyare (the five beloved) and requested them to administer the pahul (amrit chakhha) to him.
With this the difference between the Guru and the Khalsa was symbolically removed.
Guru Nanak was from the Khatri mercantile caste whereas his followers were mostly rural Jats.
Guru Gobind Singh inaugurated the Khalsa among the Sikhs.
Guru Arjan compiled the Guru Granth Sahib.
After the death of Guru Gobind Singh, the tenth Guru, the tradition of guru ended.
It was believed that the spirit of the guru did not pass onto any successor but instead remained within “Shri Gurugranth Sahib”.