For example, when the Alvar says, "I saw Kannan," the literal meaning is vision. The inner meaning (according to the PDF commentary of the 15th century) is "Acharya Upadesam" (the teaching of the master).
Nalayira Divya Prabandham (Four Thousand Divine Hymns) is a canon of 4,000 Tamil verses composed by the 12 Alvars (Vaishnava poet-saints). It is considered the "Tamil Veda" and remains a central liturgical text in Sri Vaishnavism. Digital Resources for Meanings and PDFs divya prabandham with meaning pdf