The top program provides a dynamic real-time view of a running system. It can display system summary information as well as a list of tasks currently being managed by the Linux kernel. The types of system sum-
mary information shown and the types, order and size of information displayed for tasks are all user configurable and [...]

pstree shows running processes as a tree. The tree is rooted at either pid or init if pid is omitted. If a user name is specified, all process trees rooted at processes owned by that user are shown.
pstree visually merges identical branches by putting them [...]