Virtually all jackets employ what's know as a DWR, or durable water-repellent finish, applied to the outer fabric. Like the name says, the DWR is what cause water to bead up on the shell. A three-layer construction consists of a nylon shell, the laminate, and an inner layer of wicking material, all sandwiched together. How a jacket is designed to pull apart is just as important as how it's stitched together. The more breathable the fabric, the less features that are needed or used.
Ventilation features, as much as any fabric technology, are key to a jacket's breathability.
Mesh backed pockets and underarm zippers maximize air flow, as do cuffs, waists and hems that can be adjusted to open wide. It's a great way to get some extra ventilation, even with the hatches partially battened down. A jacket should be roomy enough that you can layer underneath it and pump air through it with your body movements. For a general outdoor use, seek a cut about thigh length. The extra inches provide additional protection for your legs and your rear end-and the jacket will never gather at the waist or creep up.