Very easy effort without training effect. Very light pace you can hold indefinitely.

Easy effort in the aerobic zone. Pace you can hold for 1-2 hours. You can carry on a full conversation at this pace without gasping for air between words or sentences.

Controlled pace close to your lactate threshold which you can hold for 30-45 minutes. You are sweating but can speak a sentence at a time before having to take a gasp of breath.

Hard effort in with controlled discomfort while you are pushing into the challenging zone around your VO2 max. Pace you can hold for 15-20 minutes. You might get a word or two out, but breathing is difficult.

A very hard effort purely in the anaerobic zone. Fast pace you can hold for 3-5 minutes. Even a single word is nearly impossible to get out.

All out sprint you can only hold for a short time. You leave nothing in the tank.