To understand the difference between svayam-rupa, tad-ekatma-rupa, avesa, prabhava and vaibhava, Srila Bhaktivinoda Thakura has given the following description. In the beginning, Krsna has three bodily features: (1) svayam-rupa, as a cowherd boy in Vrndavana; (2) tad-ekatma-rupa, which is divided into svamsaka and vilasa; and (3) avesa-rupa. The svamsaka, or expansions of the personal potency, are (1) Karanodakasayi, Garbhodakasayi, Ksirodakasayi and (2) incarnations such as the fish, tortoise, boar and Nrsimha. The vilasa-rupa has a prabhava division, including Vasudeva, Sankarsana, Pradyumna and Aniruddha. There is also a vaibhava division in which there are twenty-four forms, including the second Vasudeva, Sankarsana, Pradyumna and Aniruddha. For each of these, there are three forms; therefore there are twelve forms altogether. These twelve forms constitute the predominant names for the twelve months of the year as well as the twelve tilaka marks on the body. Each of the four Personalities of Godhead expands into two other forms; thus there are eight forms, such as Purusottama, Acyuta, etc. The four forms (Vasudeva, etc.), the twelve (Kesava, etc.), and the eight (Purusottama, etc.) all together constitute twenty-four forms. All the forms are differently named in accordance with the weapons They hold in Their four hands.