An AET file is typically understood as a reusable AE template, designed so you can open it repeatedly and save new versions rather than overwrite the source, with the file storing everything that defines the motion graphic: comps, timeline structure, layer stacks, animation keyframes, effect setups, expressions, cameras/lights, render settings, plus organizational items like folders and interpretation settings.An AET typically does not include the raw media; instead it references external clips, graphics, and audio, which is why these templates are usually distributed as a ZIP with a Footage/assets directory and why After Effects may prompt for missing files if anything was moved, and because AETs may rely on specific fonts or third-party plugins, opening one on a new computer can lead to warnings until the required items are added, while remembering that file extensions aren’t exclusive, so the safest way to confirm the correct app is checking “Opens with” or considering where the file originated.An AEP file represents the editable project you’re actively working on, while an AET is a reusable template, so in practice the difference lies in purpose: you open an AEP to continue that same project, but you open an AET to start a fresh file so the original stays clean.That’s why AET files are a standard format for motion-graphics template packs (intros, lower-thirds, slideshows): the designer keeps the AET untouched as the master, and you begin each new video by opening it and doing Save As to create your AEP before customizing text, logos, colors, and media, and although both AET and AEP contain the same technical elements—compositions, layers, keyframes, effects, expressions, cameras/lights, and settings—and both refer to external footage, the AET protects the template while the AEP serves as the editable, ongoing production file.AET file opening software keeps the structure and logic of a motion-graphics project but not necessarily its media, holding compositions with their resolution, FPS, duration, and nesting order, and keeping the full layer stack—text, shapes, solids, adjustments, precomps, and placeholders—plus each layer’s settings such as position, scale, rotation, opacity, masks, mattes, blending modes, and parenting, along with all animation info including keyframes, easing curves, markers, and any motion-driving expressions.Additionally, the template captures effects and their configurations, such as color correction, blurs, glows, distortions, and transitions, together with any 3D setup—cameras, lights, 3D layer settings—and render/preview preferences, plus project structure like folders, labels, interpretation settings, and proxies, though it usually omits embedding raw media, fonts, or plugins, depending on linked paths that can lead to missing-footage or missing-effect warnings when the file is opened elsewhere.