When mesuring the flow of liquid what are the two things to measure?

There are more than two.

It depends on the mass of the liquid and the volume, and also how and where the liquid is flowing.

If you're talking about water through a tube at a 90 degree angle, that's a lot different than syrup flowing through a smaller tube at a 10 degree angle.

If you will clarify the situation, we may be able to help you further.

To determine the volume flow of liquid through a pipe you need to know (a) the cross-section area of the pipe and (b) the velocity of the liquid along in pipe. With those two bits of information you can determine the flow in terms of volume per unit time. You can then easily convert that to a measure such as liters/second or gallons/second.

you can measure the velocity then with the cross sectional area of the pipe you can calculate the flow rate on a volume basis.

The other variables that can be important is the temperature of the liquid and its gravity. With this information you can also calculate the mass flow rate.