Dalian Hongbo Electric Engineering explains the difference between butterfly valves and gate valves.

First, let's distinguish them by definition:

A gate valve is a common shut-off valve that uses a gate (the closing member; in the gate, the closing member is called the gate or gate valve, and the valve seat is called the gate seat) to connect (fully open) or shut off (fully closed) the medium in the pipeline. It should not be used for throttling, and during use, it should be avoided to slightly open the gate, as the erosion of the high-speed flowing medium will accelerate the damage of the sealing surface. The gate moves up and down on one side of the plane perpendicular to the centerline of the gate seat channel, like a gate, to cut off the medium in the pipeline, hence the name gate valve.
A butterfly valve refers to a valve where the closing member (valve flap or butterfly plate) is a disc that rotates around the valve axis to achieve opening and closing. It mainly acts as a shut-off and throttling valve in the pipeline. The closing member of a butterfly valve is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve opening and closing or regulation. The full opening to full closing of a butterfly valve is usually less than 90°. The butterfly valve and butterfly stem themselves do not have self-locking capability. To position the butterfly plate, a worm gear reducer must be added to the valve stem. Using a worm gear reducer not only gives the butterfly plate self-locking capability, allowing the butterfly plate to stop at any position, but also improves the valve's operational performance.

Secondly, from the perspective of the operation method:

Gate valves are straight-travel valves, that is, the valve stem drives the valve plate to move vertically up and down to complete the opening and closing of the gate valve. Therefore, the flow resistance of the gate valve is small, but because of its high opening height, the opening and closing speed is relatively slow.
Butterfly valves are angle-travel valves, that is, the valve plate of the butterfly valve rotates 90° around the valve axis to complete the opening and closing action. Therefore, the opening height of the butterfly valve is only one-quarter of the diameter of the passage, so it opens and closes quickly.

From the perspective of the function and application of gate valves and butterfly valves:

Gate valves have low flow resistance and good sealing performance. Because the gate valve plate and the flow direction of the medium are at a vertical angle, if the gate valve plate is not properly opened or closed, the scouring of the medium on the valve plate will cause the valve plate to vibrate, which is very easy to cause damage to the gate valve seal. Therefore, they are often used in pipelines that require strict sealing and do not need frequent opening and closing for shut-off purposes, but are not suitable for regulating pipeline medium parameters. Because of their slow opening and closing speed, they are also not suitable for emergency shut-off situations. Gate valves have a wide range of operating conditions and can be used in high-temperature, low-temperature, high-pressure, and low-pressure conditions.