It meant that for some reason a table in your database has become corrupted. In this case it is your config table which as you have discovered will cause your site to crash. Fortunately, this is a table that rarely changes as it is only written to when you change your configuration.
First thing to try is a manual repair. Usually a host provides a tool called PHPmyadmin found in your hosts cPanel. You can select the above table and use the repair option. Hopefully that will fix things.
If that fails then things get a little harder. You will first need to take a full backup of your current database. Then hopefully you will have an older backup and here is where it gets a little tricky, you will need to extract the config table from that database and replace the corrupt table in your current one. If it comes to that come back and we can advise on how to do that.