It means that you get an extra option to better match your pension to your personal (financial) situation and wishes. The amount you take out can be spent freely. Your monthly life-long pension benefits will however be lower as a result. Also, taking out an amount in a lump sum can have consequences in terms of tax and any allowances or other benefits.
Here you can read more if you opt for a lump sum and what you need to pay attention to. You will also find our answers to frequently asked questions. Check here for other options you have for your pension.