Question:

Why is our generation sometimes referred to as the "Footsteps of Moshiach"? 

Answer:

Our generation is spiritually inferior to the preceding generations, and the G-dly energy is least manifest in the world, compared to previous times.

The expression "footsteps of Moshiach" is first cited in Talmud, Tractate Sota.  Rashi explains that the term refers to "the time period towards the end of exile, immediately before the redemption."

The term has a dual connotation.  The foot is the lowest part of the body and shows the least vitality.  Our generation is spiritually inferior to the preceding generations, and the G-dly energy is least manifest in the world, compared to previous times.

On the other hand, the term also alludes to the fact that we are close to redemption, to the point that we can already hear the footsteps of Moshiach approaching.  Apparently, the two meanings of this expression contradict one another.  The first indicates our spiritual lowliness, while the second relates to how close we are to redemption.

However, the Lubavitcher Rebbe draws a connection between the two interpretations.  He explains that although our generation is indeed spiritually lower than previous generations, we are actually an extension of them.  If our generation was measured according to its own merits, we would indeed be found inferior.  However, just like the foot is contiguous with the rest of the body, our generation has all the merits and strengths of the previous generations. 

Although our generation is spiritually lowest, we are the ones who will merit the Redemption.  Therefore, we can already sense and hear the "footsteps" of Moshiach approaching.  Just as the foot bears the weight of the entire body and carries it to its destination, our generation will carry all the previous generations along with us as we go forth to greet Moshiach.