Open Settings, then Wording. There are eight nouns you can change, each with a singular and a plural.
The eight are Deal, Organisation, Person, Project, Quote, Activity, Ticket and Pipeline.
What changes and what does not
Changing a word updates the app for everyone at once, immediately. It renames the objects only: nothing moves, nothing is lost, and no report has to be rebuilt.
It reaches the mobile apps too, so a plumber sees "Jobs" on their phone and in the office.
What it does not change is anything you have typed yourself. A project you named "Deal review" keeps that name, because it is your text and not ours.
Starting again
If you have edited yourself into a mess, the same screen offers the complete word set from any of the ten business setups. Take one wholesale and it overwrites all eight at once, which is usually faster than unpicking what you changed.