"Outdoor" knives would be hunting knives, pocket knives, tactical knives, military knives, etc. They generally have a wider profile than kitchen knives, because they are used with greater force and with harder materials (like cutting through hide or wood) so they need a greater shoulder strength to hold up to the task. Kitchen knives and fillet knives generally have a narrower profile, in the range of 16 to 20 degrees from center. The narrower profile means they can be made a bit sharper than outdoor knives, but they don't have the shoulder strength to hold up to tougher jobs. So kitchen knives and fillet knives are used for meats, vegetables and fruit, but not for skinning game or whittling wood, for example. Outdoor knives generally have a profile between 22.5 and 30 degrees from center, 25 degrees being most common.

A bit more clarification: So the reason they're called "Outdoor" knives is because they're generally used outdoors. Kitchen knives have a different profile and so are sharpened with a different angle guide, and they generally aren't used outdoors. So we have a separate section in the User Guide for them, and separate videos. Simple!