What's the main difference between a "trash pump" and "high-pressure pump"?

There is a significant difference between using a trash pump compared to a high-pressure pump when providing water to your big sprinkler(s).

A trash pump is designed to have a large flow rate with a low amount of pressure. A high-pressure pump is designed to move water with much higher levels of pressure.

For example, a two-inch trash pump pumps 50 gpm at 35 psi. While a two-inch high-pressure pump will pump 50 gpm at 65 psi. For your big sprinkler to run at its peak performance, the flow rate needs to be delivered to the sprinkler with high pressure.