Explanation:

• The Bhakti movement was an important historical religious movement in medieval Hinduism that sought to bring religious reforms to all strata of society by adopting the method of devotion to achieve salvation.
• Saguna represented those poet-saints who composed verses extolling a god with attributes or form.
• Nirguna represented those poet-saints who extolled God without and beyond all attributes or form. They are also known as Monotheistic Bhakti saints.
• Nayanars were devoted to Lord Shiva and his avatars.
• Alvars were devoted to Lord Vishnu and his avatars.

Source: UPSC CDS