Two straight lines are parallel to each other if they cannot meet, however far produced.
Two planes are parallel to each other if they cannot meet, however far produced.
Look at the following cube and find:
a) Two coplanar lines.
b) A line and a plane parallel to each other.
c) Two planes parallel each other 

Solution:
a) Two coplanar lines:

b) A line and a plane parallel to each other:
CDHG
c) Two planes parallel each other: ABCDEFGH, AEHGBFGC, ABFEDCGH