What's the difference between a PCR primer and a sequencing Primer

[ilovescience]

I understand that the following is true :

You can use the same primer for PCR and sequencing. They do not have any differences and you look for the following characteristics:

- 20 base pairs long
- 40-60% G/C composition
- separated by around 500 base pairs (best for sequencing)

It works well for both application. You amplify the fragment by PCR, isolate it, and sequence it with the same primer.
4 years ago

However, when asked to design a pair of PCR primers and two sequencing primers that would allow you to sequence something in both directions. All the primers should be 20 base pairs in length and the sequencing primers should prime at least 50 base pairs from the target sequence.

what exactly does that bold bit mean?

thank you.