The two devices do different things - and the names describe them well.
if you have a pipeline that has a long vertical drop, the static pressure at the lower end of the pipe might be so great that the pipe will burst. To prevent this, a small tank is built somewhere along the pipeline. The upper part of the pipeline discharges into this tank. The tank then discharges into the lower pipeline. The static pressure At the bottom of the pipeline is now measured from the break pressure tank rather than the top of the pipeline.
Air release valves allow air to leak out of a pipeline but keep the water in the pipe. Air gets entrapped in the water and can gather in the pipe, often at high points, for example as a pipe crosses over a river.
I hope this is useful