Ajam nirvikalpam nirakaaramekam
Niraanandam anandam advaita purnam
Param nirgunam nirvishesham nireeham
Para brahma roopam Ganesham bhajema.
We know Ganesha with a form. Ganesha here is being symbolized as a manifestation of that Para Brahman with no forms, definitions nirvikalpam, nirakararoopam, or impurities, nirmalam. Anandam, advaitam and purnam are a description of the Supreme Brahman. So, we bow down to Ganesha, the manifestation of the Supreme.