Rates, and what an hour is worth
Set an hourly rate per person and Vylan can put a value on the time your firm records. Without rates you still get hours — you simply do not get dollars, which is the honest answer rather than zero.
Hours on their own answer "where did the week go". Hours with a rate on them answer "is this client worth what we charge them", which is the question that actually changes what a firm does.
Setting them
Rates are per person and live with the rest of your team's settings — Set rates in team settings is the shortcut from the insights screen itself.
A rate applies from when you set it. Changing somebody's rate does not rewrite what their past hours were worth, which is what you want: last quarter's numbers should not move because of a raise this quarter.
What happens with no rate
Time recorded by somebody with no rate carries no money value at all. It is left out of a dollar total rather than counted as nothing.
This matters more than it sounds. Counting an unrated hour as $0 would quietly report that the work was worthless, and a firm reading a profitability number would be reading a number built partly from people it never priced. Hours you can see, dollars you cannot — that is the truthful version, and where a total is built from a mix, it is marked Estimated.
Rates are for valuing time. What you actually charge a client is set on the engagement and its invoice — see creating an invoice.