As stated before, the topic of conformation requires further investigation.  From the previous section, you may remember the Newman Projection of the staggered form of ethane:

Staggered

However, this is just one conformation of ethane, albeit the one of lowest energy.  As previously stated, there are an infinite number of possible conformations of ethane, however, a few are of interest and have specific names.

Eclipsed

Clearly, as the name suggests, this conformation has all the hydrogen atoms in line with each other, so that the rear atoms are eclipsed by the front ones.  However, to make it clear which molecule we are dealing with in our representation, the rear atoms are drawn slightly to one side. 

This conformation is of highest energy, as the C-H bonds are all as close as possible. This is exactly the opposite situation to the staggered form, where all the C-H bonds have their maximum separation, and hence the staggered form is of lowest energy.

There also exist some important conformations of intermediate energy, though these are best described with molecules other than ethane. Let us have a look at the conformations of 1,2 dibromoethane:

Above, we can see, the lowest energy form; staggered with the two bromine atoms as far from each other as possible (antiperiplanar in this case), and two slightly higher energy forms, which look staggered, but are higher in energy because the bromine atoms are near each other.

There are also more eclipsed versions in this molecule:

The highest energy form is the fully eclipsed form, where the two bromine atoms eclipse each other, and the slightly lower energy form is just called eclipsed, and has a bromine eclipsing a hydrogen atom.

All these forms can only be considered distinct because there is a barrier to rotation about the axial bond in each case.  If all the forms had the same energy, the molecule would rotate freely about its axis at any temperature. 

However, as it is, due to the the increase in energy when atoms eclipse (which is caused by the eclipsing of the electrons in the bonds to those atoms), the molecules above do not have free rotation at all temperatures.  (Note that in reality, because the energy barrier is only very small, the temperature must be very low indeed to prevent rotation in ethane for example, and at room temperature, ethane does rotate freely and very rapidly.)