Level 1: You can ride a bike but you're new to mountain biking. It looks like fun, but you want some help tackling the challenges that off-road riding has to offer, learning more about your bike, and the etiquette for the sport.
Level 2: Smooth, rolling trails are fun for you, but you're not totally confident when it gets rougher with rocks and roots to navigate. Getting better on corners and rougher terrain are goals for you.
Level 3: You're able to ride most trails, but get a bit of pucker factor on the more advanced trails. You're ready to start pushing your riding, finding new lines, and getting smoother in the rough stuff. Some air time wouldn't be bad either.
Level 4: Jumps, drops, technical riding? No problem. Improvements will come from refining your technique and getting more playful and smoother in all types of terrain. Building your performance will get you going faster and bigger.
Level 1: You exercise a few times per month. Casual bike rides are cool, but hills and wind are avoided.
Level 2: You're a weekend warrior, exercising a couple of times a week and getting out riding a few times per month.
Level 3: You're happy to attack a few climbs per ride, exercise a few times a week and stay active regularly.
Level 4: Hard exercise is something you look forward to, and your friends call you "super fit". You ride nearly daily and push the pace when you do.