A permalink is the individual link to each blog post. You want to make sure that your permalinks are search engine friendly. Accomplish this by having blog post titles, not dates.
Notice the text that appears after the forward slash in your URL (the orange part in the example below):
You don't want post numbers or dates:
You'll want to make sure you change your permalink structure to "post names" before you start writing any post. This way your permalinks don't have dates associated to them and will be more search engine friendly. This is important.
Here's how to do it:
This will save you from the headache of creating new URLs and re-directs down the road. (A re-direct is when you point an old post from one URL to a new URL address, so when someone types in the old web address they will still find the page that you moved.)