He meets David in the Digital World after he travels with his brother and Damemon, the two then precede to become best friends. While Labramon may look the weakest of the group he has the ability to become strongest.
The name "Labramon" refers only to the Rookie form of this Digimon. Throughout the series, Labramon gains the ability to digivolve into a number of more powerful forms, each with a different name and special attack. However, the Rookie level is his preferred one and the one he spends most of his time in.
Labramon's Champion form and very powerful. He can Digivolve into Seasarmon from the beginning of the story, and is one of the groups most powerful Champion Level Digimon.
Labramon's Ultimate form. More information to be released when Labramon Evolves into Caturamon.