The Footprint of the Buddha (Buddhapada) is an important symbol of the Buddha and is commonly found in Buddhist temples, especially in Sri Lanka and Thailand.  Early Buddhist art is known to be devoid of human forms with the Buddha typically being represented by symbols such as the footprint or empty throne. 

In Buddhist suttas and early commentaries, there were also mentions of the Buddha’s feet.

In the Lakkhana Sutta (Discourse of the Marks), the 32 characteristics of a Great Man were described by the Buddha to His congregation at Jetavana.  Here, the Buddha described one of the characteristics to be wheels with a thousand spokes on the soles of the Great Man.

In the Narasihagatha, the princess Yasodhara described to her son Rahula the features of Rahula’s father (the Buddha) and when it comes to his feet,  

His red sacred feet are marked with an excellent wheel;

His long heels are decked with characteristic marks;

His feet are adorned with chowrie (camara)* and parasol.

That indeed, is your father, the lion of men.

*Camara - flywhisk

In early depictions of the Footprint (early Indian and Sinhalese Footprints), there were few auspicious symbols on the Footprint.  Over the centuries, the signs on the footprint grew to 108 in number.  Some of the symbols include the satti (spear – symbol of power or Enlightenment), the svastika (auspiciousness), the sun, the moon, the great mountain ranges and the ocean.  The signs on the feet can differ between cultures and different time eras.

The Buddha’s Footprint is an important symbol to Buddhists as we aspire to follow Buddha’s on His Path to Enlightenment. 

The footprints of the Buddha symbolize the Buddha's presence, as they are believed to be the imprints where the Buddha actually touched the ground. At the same time, the Buddhapada signify the Buddha's absence now that he has entered nirvana, and thus are a reminder of the Buddhist ideal of nonattachment.

(extract from http://www.religionfacts.com/buddhapada)

More information on the Footprint

https://www.buddhanet.net/e-learning/history/b_feet.htm