Baobab is an editor for large phylogenetic trees written in Java.
Tree editor means that it allows you to create and/or modify a tree interactively, adding/(re)moving branches and nodes, changing leave names, setting parameters. Baobab focuses on edition, not representation and display that are only used as a tool to make edition easier.
Large means that Baobab includes tools to simplify the task of managing heavy dataset (typically dealing with several hundred species).