What does "soft limit" and "hard limit" mean?

If your plan reaches its usage limit, it will trigger an action in our system. The Hobby plan has a 'hard limit' which means that when a limit has been reached, the tool which has exceeded the limit will become unavailable for the rest of the month. All other plans have 'soft limits', which will not result in any tools becoming unavailable. If a soft limit is reached in any paid plan, our system will notify the account administrator and suggest a plan upgrade.