confused with these

[SangFroid]

1. In how many ways can 6 of 11 different trees be planted along the side of a river?

2. In how many ways can a sample of 4 chocolates be selected from a box of 12 chocolates?

( i know both these are simple ones...but i am confused about the difference between these... pls enlighten me )

[dsaqwert]

.....

1. In how many ways can 6 of 11 different trees be planted along the side of a river?
11p6
2. In how many ways can a sample of 4 chocolates be selected from a box of 12 chocolates?
12c4
( i know both these are simple ones...but i am confused about the difference between these... pls enlighten me )

[Blase]

My

1. In how many ways can 6 of 11 different trees be planted along the side of a river?

2. In how many ways can a sample of 4 chocolates be selected from a box of 12 chocolates?

( i know both these are simple ones...but i am confused about the difference between these... pls enlighten me )